Sentinel-2 is a multispectral
operational imaging mission within the GMES (Global Monitoring for
Environment and Security) program, jointly implemented by the EC
(European Commission) and ESA (European Space Agency) for global land
observation (data on vegetation, soil and water cover for land, inland
waterways and coastal areas, and also provide atmospheric absorption
and distortion data corrections) at high resolution with high revisit
capability to provide enhanced continuity of data so far provided by
SPOT-5 and Landsat-7. 1)2)3)4)5)6)7)8)

Copernicus is the new name of the European Commission's Earth Observation Programme, previously known as GMES
(Global Monitoring for Environment and Security). The new name was
announced on December 11, 2012, by EC (European Commission)
Vice-President Antonio Tajani during the Competitiveness Council.

In the words of Antonio
Tajani: “By changing the name from GMES to Copernicus, we are
paying homage to a great European scientist and observer: Nicolaus
Copernicus (1473-1543). As he was the catalyst in the 16th
century to better understand our world, so the European Earth
Observation Programme gives us a thorough understanding of our changing
planet, enabling concrete actions to improve the quality of life of the
citizens. Copernicus has now reached maturity as a programme and all
its services will enter soon into the operational phase. Thanks to
greater data availability user take-up will increase, thus contributing
to that growth that we so dearly need today.”

The mission is dedicated to the full
and systematic coverage of land surface (including major islands)
globally with the objective to provide cloud-free products typically
every 15 to 30 days over Europe and Africa. To achieve this objective
and to provide high mission availability, a constellation of two
operational satellites is required, allowing to reach a 5-day
geometric revisit time. The revisit time with only one operational
satellite as it will be the case at the beginning of the deployment of
the system is 10 days. - In comparison, Landsat-7 provides a 16-day
geometric revisit time, while SPOT provides a 26-day revisit, and
neither of them provides systematic coverage of the overall land
surface.

The following list summarizes the top-level system design specifications derived from the user requirements:

• Sentinel-2 will provide
continuity of data for services initiated within the GSE (GMES Service
Element) projects. It will establish a key European source of data for
the GMES Land Fast Track Monitoring Services and will also contribute
to the GMES Risk Fast Track Services.

• The frequent revisit and
high mission availability goals call for 2 satellites in orbit at a
time, each with a 290 km wide swath using a single imaging instrument

•
Continuous land + islands carpet mapping imaging within the latitude
range of -56º to +83º (the selected orbit excludes imagery
from Antarctica)

• An accurate geolocation
(< 20 m) of the data is required (without GCPs) and shall be
produced automatically to meet the timeliness requirements. The
geolocation accuracy of Level 1 b imagery data w.r.t. WGS-84 (World
Geodetic System - 1984) reference Earth ellipsoid of better than 20 m
at 2σ confidence level without need of any ground control points
is required.

• Very good radiometric image quality (combination of onboard absolute and on ground vicarious calibration).

• The mission lifetime is
specified as 7.25 years and propellant is to be sized for 12 years,
including provision for de-orbiting maneuvers at end-of-life.

To provide operational services over
a long period (at least 15 years following the launch of the first
satellites), it is foreseen to develop a series of four satellites,
with nominally two satellites in operation in orbit and a third one
stored on ground as back-up.

In partnership: The
Sentinel-2 mission has been made possible thanks to the close
collaboration between ESA, the European Commission, industry, service
providers and data users. Demonstrating Europe’s technological
excellence, its development has involved around 60 companies, led by
Airbus Defence and Space in Germany for the satellites and Airbus
Defence and Space in France for the multispectral instruments. 10)

The mission has been supported in
kind by the French space agency CNES to provide expertise in image
processing and calibration, and by the German Aerospace Center DLR that
provides the optical communication payload, developed by Tesat Spacecom
GmbH.

This piece of technology allows the
Sentinel-2 satellites to transmit data via laser to satellites in
geostationary orbit carrying the European Data Relay System (EDRS).
This new space data highway allows large volumes of data to be relayed
very quickly so that information can be even more readily available for
users.

Seven years in the making, this
novel mission has been built to operate for more than 20 years.
Ensuring that it will meet users’ exacting requirements has been
a challenging task. Developing Sentinel-2 has involved a number of
technical challenges, from early specification in 2007 to qualification
and acceptance in 2015.

The satellite requires excellent
pointing accuracy and stability and, therefore, high-end orbit and
attitude control sensors and actuators. The multispectral imager is the
most advanced of its kind, integrating two large visible near-infrared
and shortwave infrared focal planes, each equipped with 12 detectors
and integrating 450,000 pixels.

Pixels that may
fail in the course of the mission can be replaced by redundant pixels.
Two kinds of detectors integrate high-quality filters to isolate the
spectral bands perfectly. The instrument’s optomechanical
stability must be extremely high, which has meant the use of silicon
carbide ceramic for its three mirrors and focal plane, and for the
telescope structure itself.

The geometric performance requires
strong uniformity across the focal planes to avoid image distortion.
The radiometric performance excluded any compromise regarding stray
light, dictating a tight geometry and arrangement of all the optical
and mechanical elements. The instrument is equipped with a calibration
and shutter mechanism that integrates a large spectralon sunlight
diffuser.

Each satellite has a high level of
autonomy, so that they can operate without any intervention from the
ground for periods of up to 15 days. This requires sophisticated
autonomous failure analysis, detection and correction on board.

The ‘carpet mapping’
imaging plan requires acquisition, storage and transmission of 1.6 TB
per orbit. This massive data blast results from the combination of the
290 km swath with 13 spectral channels at a spatial resolution as high
as 10 m.

In addition, the optical
communication payload using the EDRS data link is a new technology that
will improve the amount and speed of data delivery to the users. This
was very recently demonstrated by Sentinel-1A, which also carries an
optical communication payload.

Land in focus: Ensuring that
land is used sustainably, while meeting the food and wood demands of a
growing global population – a projected eight billion by 2020
– is one of today’s biggest challenges. The Copernicus land
service provides information to help respond to global issues such as
this as well as focusing on local matters, or ‘hotspots’,
that are prone to specific challenges.

However, this service relies on very
fast revisit times, timely and accurate satellite data in order to make
meaningful information available to users – hence, the role of
Sentinel-2. Through the service, users will have access to information
about the health of our vegetation so that informed decisions can be
made – whether about addressing climate change or how much water
and fertilizer are needed for a maximum harvest.

Sentinel-2 is able to distinguish
between different crop types and will deliver timely data on numerous
plant indices, such as leaf area index, leaf chlorophyll content and
leaf water content – all of which are essential to accurately
monitor plant growth. This kind of information is essential for
precision farming: helping farmers decide how best to nurture their
crops and predict their yield.

While this has obvious economic
benefits, this kind of information is also important for developing
countries where food security is an issue. The mission’s fast
geometric revisit of just five days, when both satellites are
operational, and only 10 days with Sentinel-2A alone, along with the
mission’s range of spectral bands means that changes in plant
health and growth status can be easily monitored.

Sentinel-2 will also provide
information about changes in land cover so that areas that have been
damaged or destroyed by fire, for example, or affected by
deforestation, can be monitored. Urban growth also can be tracked.

The Copernicus services are managed
by the European Commission. The five ‘pan-European’ themes
covering 39 countries are addressed by the land service, including
sealed soil (imperviousness), tree cover density, forest type, and
grasslands. There is currently insufficient cloud-free satellite data
in high resolution with all the necessary spectral bands that cover
Europe fast enough to monitor vegetation when it is growing rapidly in
the summer. Sentinel-2 will fill this gap.

This multi-talented mission will
also provide information on pollution in lakes and coastal waters at
high spatial resolution and with frequent coverage. Frequent coverage
is also key to monitoring floods, volcanic eruptions and landslides.
This means that Sentinel-2 can contribute to disaster mapping and
support humanitarian aid work.

Leading edge: The span of 13
spectral bands, from the visible and the near-infrared to the shortwave
infrared at different spatial resolutions ranging from 10 to 60 m on
the ground, takes global land monitoring to an unprecedented level.

The four bands at 10 m resolution
ensure continuity with missions such as SPOT-5 or Landsat-8 and address
user requirements, in particular, for basic land-cover classification.
The six bands at 20 m resolution satisfy requirements for enhanced
land-cover classification and for the retrieval of geophysical
parameters. Bands at 60 m are dedicated mainly to atmospheric
corrections and cirrus-cloud screening.

In addition, Sentinel-2 is the first
civil optical Earth observation mission of its kind to include three
bands in the ‘red edge’, which provide key information on
the vegetation state.

Thanks to its high temporal and
spatial resolution and to its three red edge bands, Sentinel-2 will be
able to see very early changes in plant health. This is particularly
useful for the end users and policy makers to detect early signs of
food shortages in developing countries (Ref. 10).

In April 2008, ESA awarded the prime
contract to Airbus Defence and Space (former EADS-Astrium GmbH) of
Friedrichshafen, Germany to provide the first Sentinel-2A Earth
observation satellite. In the Sentinel-2 mission program, Astrium is
responsible for the satellite’s system design and platform, as
well as for satellite integration and testing. Astrium Toulouse will
supply the MSI (MultiSpectral Instrument), and Astrium Spain is in
charge of the satellite’s structure pre-integrated with its
thermal equipment and harness. The industrial core team also comprises
Jena Optronik (Germany), Boostec (France), Sener and GMV (Spain). 11)12)13)14)

In March 2010, ESA and EADS-Astrium
GmbH signed another contract to build the second Sentinel-2
(Sentinel-2B) satellite, marking another significant step in the GMES
program. 15)16)17)

Sentinel-2 uses the AstroBus-L of
EADS Astrium, a standard modular ECSS (European Cooperation for Space
Standards) compatible satellite platform compatible with an in-orbit
lifetime of up to 10 years, with consumables sizeable according to the
mission needs. The platform design is one-failure tolerant and the
standard equipment selection is based on minimum Class 2 EEE parts,
with compatibility to Class 1 in most cases. The AstroBus-L platform is
designed for direct injection into LEO (Low Earth Orbit). Depending on
the selection of standard design options, AstroBus-L can operate in a
variety of LEOs at different heights and with different inclinations.
An essential feature of AstroBus-L is the robust standard FDIR (Failure
Detection, Isolation and Recovery) concept, which is hierarchically
structured and can easily be adapted to specific mission needs.

The satellite is
controlled in 3-axes via high-rate multi-head star trackers, mounted on
the camera structure for better pointing accuracy and stability, and
gyroscopes and a GNSS receiver assembly. The AOCS (Attitude and Orbit
Control Subsystem) comprises the following elements: 18)

• A dual frequency GPS receiver (L1/L2 code) for position and time information

The geolocation accuracy
requirements of < 20 m for the imagery translate into the following
AOCS performance requirements as stated in Table 4.

Attitude determination error (onboard knowledge)

≤ 10 µrad (2σ) per axis

AOCS control error

≤ 1200 µrad (3σ) per axis

Relative pointing error

≤ 0.03 µrad/1.5 ms (3σ); and ≤ 0.06 µrad/3.0 ms (3σ)

Table 4: AOCS performance requirements in normal mode

For Sentinel-2
it was decided to mount both the IMU and the star trackers on the
thermally controlled sensor plate on the MSI. So the impact of
time-variant IMU/STR misalignment on the attitude performance can be
decreased to an absolute minimum. Furthermore, the consideration of the
time-correlated star tracker noises by covariance tuning was decided.

• Solar Array (one deployable and rotatable single wing with three panels). Total array area of 7.1 m2.
Use of 2016 triple junction GaAs solar cells with integrated diode.
Total power of 2300 W (BOL) and 1730 W (EOL). The mass is < 40 kg.

The spacecraft mass is ~ 1200 kg,
including 275 kg for the MSI instrument, 35 kg for the IR payload
(optional) and 80 kg propellant (hydrazine). The S/C power is 1250 W
max, including 170 W for the MSI and < 100 W for the IR payload. The
spacecraft is designed for a design life of 7.25 years with propellant
for 12 years of operations, including deorbiting at EOL (End of Life).

Payload data are being stored in NAND flash memory technology SSR (Solid State Recorder) based on integrated CoReCi
(Compression Recording and Ciphering) units of Airbus DS, available at
various capacities. The CoReCi is an integrated image compressor, mass
memory and data ciphering unit designed to process, store and format
multi-spectral video instrument data for the satellite downlink. The
mass memory utilizes high performance commercial Flash components, ESA
qualified and up-screened for their use in space equipment. This new
Flash technology allows mass and surface area used in the memory to be
reduced by a factor of nearly 20 when compared with the former SD-RAM
(Synchronous Dynamic Random Access Memory) based equipment. The first
CoReCi unit has been successfully operating on SPOT-6 since September
2012. Sentinel-2A is carrying a CoReCi unit. 19)20)

The MRCPB (Multi-Résolution
par Codage de Plans Binaires) compression algorithm used is a wavelet
transform with bit plane coding (similiar to JPEG 2000). This complex
algorithm is implemented in a dedicated ASIC, with speeds of up to 25
Mpixel/s. Alternatively this unit can be supplied with a CCSDS
compression algorithm using a new ASIC developed with ESA support. The
ciphering is based on the AES algorithm with 128 bit keys. The
modularity of the design allows the memory capacity and data rate to be
adapted by adjusting the number of compressor and memory boards used.

Development status:

• February 27, 2017: The ninth
Vega light-lift launcher is now complete at the Spaceport, with its
Sentinel-2B Earth observation satellite installed atop the four-stage
vehicle in preparation for a March 6 mission from French Guiana. 21)

•
January 12, 2017: Sentinel-2B arrived at Europe’s spaceport in
Kourou, French Guiana on 6 January 2017 to be prepared for launch.
After being moved to the cleanroom and left for a couple of days to
acclimatise, cranes were used to open the container and unveil the
satellite. Over the next seven weeks the satellite will be tested and
prepared for liftoff on a Vega rocket. 22)

• November 15, 2016:
Sentinel-2B has successfully finished its test program at ESA/ESTEC in
Noordwijk, The Netherlands. The second Sentinel-2 Airbus built
satellite will now be readied for shipment to the Kourou spaceport in
French Guiana begin January 2017. It is scheduled for an early March
2017 lift-off on Vega. 23)

- Offering "color vision" for the
Copernicus program, Sentinel-2B like its twin satellite Sentinel-2A
will deliver optical images from the visible to short-wave infrared
range of the electromagnetic spectrum. From an altitude of 786 km, the
1.1 ton satellite will deliver images in 13 spectral bands with a
resolution of 10, 20 or 60 m and a uniquely large swath width of 290
km.

• June 15, 2016: Airbus DS
completed the manufacture of the Sentinel-2B optical satellite; the
spacecraft is ready for environmental testing at ESA/ESTEC. The
Sentinel-2 mission, designed and built by a consortium of around 60
companies led by Airbus Defence and Space, is based on a constellation
of two identical satellites flying in the same orbit, 180° apart
for optimal coverage and data delivery. Together they image all
Earth’s land surfaces, large islands, inland and coastal waters
every five days at the equator. Sentinel-2A was launched on 23 June
2015, its twin, Sentinel-2B, will follow early next year. 24)

- The Sentinel-1 and -2 satellites
are equipped with the Tesat-Spacecom’s LCT (Laser Communication
Terminal). The SpaceDataHighway is being implemented within a
Public-Private Partnership between ESA and Airbus Defence and Space.

• April 27, 2015: The
Sentinel-2A satellite on Arianespace’s next Vega mission is being
readied for pre-launch checkout at the Spaceport, which will enable
this European Earth observation platform to be orbited in June from
French Guiana. — During activity in the Spaceport’s S5
payload processing facility, Sentinel-2A was removed from the shipping
container that protected this 1,140 kg class spacecraft during its
airlift from Europe to the South American launch site. With Sentinel-2A
now connected to its ground support equipment and successfully switched
on, the satellite will undergo verifications and final preparations for
a scheduled June 11 liftoff. 25)

Figure 9: Sentinel-2A is
positioned in the Spaceport’s S5 payload processing facility for
preparation ahead of its scheduled June launch on Vega (image credit:
Arianespace)

• April
23, 2015: The Sentinel-2A satellite has arrived safe and sound in
French Guiana for launch in June. The huge Antonov cargo aircraft that
carried the Sentinel-2A from Germany, touched down at Cayenne airport
in the early morning of 21 April. 26)

• April 8, 2015: The
Sentinel-2A satellite is now being carefully packed away in a special
container that will keep it safe during its journey to the launch site
in French Guiana. The satellite will have one final test, a ‘leak
test’, in the container to ensure the propulsion system is tight.
Bound for Europe’s Spaceport in French Guiana, Sentinel-2A will
leave Munich aboard an Antonov cargo plane on 20 April. Once unloaded
and unpacked, it will spend the following weeks being prepared for
liftoff on a Vega rocket. 27)

• February 24, 2015:
Sentinel-2A is fully integrated at IABG’s facilities in
Ottobrunn, Germany before being packed up and shipped to French Guiana
for a scheduled launch in June 2015. 28)

• In
August 2014, Airbus Defence and Space delivered the Sentinel-2A
environmental monitoring satellite for testing . In the coming months,
the Sentinel-2A satellite will undergo a series of environmental tests
at IABG, Ottobrunn, Germany, to determine its suitability for use in
space. 29)30)

- Sentinel-2A
is scheduled to launch in June 2015; Sentinel-2B, which is identical in
design, is set to follow in March 2017. Together, these two satellites
will be able to capture images of our planet’s entire land
surface in just five days in a systematic manner.

Launch: The Sentinel-2A spacecraft was launched on June 23, 2015 (1:51:58 UTC) on a Vega vehicle from Kourou. 32)33)

RF communications: The
payload data handling is based on a 2.4 Tbit solid state mass memory
and the payload data downlink is performed at a data rate of 560 Mbit/s
in X-band with 8 PSK modulation and an isoflux antenna, compliant with
the spectrum bandwidth allocated by the ITU (international
Telecommunication Union).

Command and control of the
spacecraft (TT&C) is performed with omnidirectional S-band antenna
coverage using a helix and a patch antenna. The TT&C S-band link
provides 64 kbit/s in uplink (with authenticated/encrypted commands)
and 2 Mbit/s in downlink..

In parallel to the RF communications, an optical LEO-GEO communications link using the LCT
(Laser Communication Terminal) of Tesat-Spacecom (Backnang, Germany)
will be provided on the Sentinel-2 spacecraft. The LCT is based on a
heritage design (TerraSAR-X) with a transmit power of 2.2 W and a
telescope of 135 mm aperture to meet the requirement of the larger link
distance. The GEO LCT will be accommodated on AlphaSat of ESA/industry
(launch 2012) and later on the EDRS (European Data Relay Satellite)
system of ESA. The GEO relay consists of an optical 2.8 Gbit/s (1.8
Gbit/s user data) communication link from the LEO to the GEO satellite
and of a 600 Mbit/s Ka-band communication link from the GEO satellite
to the ground. 34)

To meet the user requirements of fast data delivery, DLR (German Aerospace Center) is funding the OCP
(Optical Communication Payload), i.e. the LCT of Tesat, – a new
capability to download large volumes of data from the Sentinel-2 and
Sentinel-1 Earth observation satellites - via a data relay satellite
directly to the ground. A contract to this effect was signed in October
2010 between ESA and DLR. 35)

Since the Ka-band downlink is the
bottleneck for the whole GEO relay system, an optical ground station
for a 5.625 Gbit/s LEO-to-ground and a 2.8 Gbit/s GEO-to-ground
communication link is under development.

Orbit: Sun-synchronous orbit,
altitude = 786 km, inclination = 98.5º, (14+3/10 revolutions/day)
with 10:30 hours LTDN (Local Time at Descending Node). This local time
has been selected as the best compromise between cloud cover
minimization and sun illumination.

The orbit is fully consistent with
SPOT and very close to the Landsat local time, allowing seamless
combination of Sentinel-2 data with historical data from legacy
missions to build long-term temporal series. The two Sentinel-2
satellites will be equally spaced (180º phasing) in the same
orbital plane for a 5 day revisit cycle at the equator.

The Sentinel-2 satellites will
systematically acquire observations over land and coastal areas from
-56° to 84° latitude including islands larger 100 km2,
EU islands, all other islands less than 20 km from the coastline, the
whole Mediterranean Sea, all inland water bodies and closed seas. Over
specific calibration sites, for example DOME-C in Antarctica,
additional observations will be made. The two satellites will work on
opposite sides of the orbit (Figure 13).

Launch: The Sentinel-2B
spacecraft was launched on March 7, 2017 (01:49:24UTC) on a Vega
vehicle of Arianespace from Europe's Spaceport in Kourou, French
Guiana. 36)37)38)39)

• The first stage separated 1
min 55 seconds after liftoff, followed by the second stage and fairing
at 3 min 39 seconds and 3 min 56 seconds, respectively, and the third
stage at 6 min 32 seconds.

• After
two more ignitions, Vega’s upper stage delivered Sentinel-2B into
the targeted Sun-synchronous orbit. The satellite separated from the
stage 57 min 57 seconds into the flight.

• Telemetry links and attitude
control were then established by controllers at ESOC in Darmstadt,
Germany, allowing activation of Sentinel’s systems to begin. The
satellite’s solar panel has already been deployed.

• After this first
‘launch and early orbit’ phase, which typically lasts three
days, controllers will begin checking and calibrating the instruments
to commission the satellite. The mission is expected to begin
operations in three to four months.

Sentinel-2B will join its sister
satellite Sentinel-2A and the other Sentinels part of the Copernicus
program, the most ambitious Earth observation program to date.
Sentinel-2A and -2B will be supplying ‘color vision’ for
Copernicus and together they can cover all land surfaces once every
five days thus optimizing global coverage and the data delivery for
numerous applications. The data provided by these Sentinel-2 satellites
is particularly suited for agricultural purposes, such as managing
administration and precision farming.

With two satellites in orbit it will
take only five days to produce an image of the entire Earth between the
latitudes of 56º south and 84º north, thereby optimizing the
global coverage zone and data transmission for numerous applications.

To ensure data continuity two
further optical satellites, Sentinel-2C and -2D, are being constructed
in the cleanrooms of Airbus and will be ready for launch as of
2020/2021.

Figure 15: This technical view
of the Sentinel-2 satellite shows all the inner components that make up
this state-of-the-art high-resolution multispectral mission (video
credit: ESA/ATG medialab)

Figure 16: As well as imaging in
high resolution and in different wavelengths, the key to assessing
change in vegetation is to image the same place frequently. The
Sentinel-2 mission is based on a constellation of two satellites
orbiting 180° apart, which along with their 290 km-wide swaths,
allows Earth’s main land surfaces, large islands, inland and
coastal waters to be covered every five days. This is a significant
improvement on earlier missions in the probability of gaining a
cloud-free look at a particular location, making it easier to monitor
changes in plant health and growth (video credit: ESA/ATG medialab)

Note: As of May 2019, the previously
single large Sentinel-2 file has been split into two files, to make the
file handling manageable for all parties concerned, in particular for
the user community.

• This article covers the Sentinel-2 mission and its imagery in the period 2019

• September 10, 2019: Australia
is tackling multiple bushfires that have broken out across New South
Wales and Queensland over the past few days. 40)

- The flames, which were said to
have been whipped up by strong winds, have now been contained. More
than 600 firefighters have been deployed to tackle the fires, and
multiple homes and outbuildings have been damaged.

Figure 17:
In this image captured by the Copernicus Sentinel-2 mission on 8
September, fires burning in the Yuraygir National Park and Shark Creek
area are visible. Fires are also burning to the north and south of the
villages of Angourie and Wooloweyah (image credit: ESA, the image
contains modified Copernicus Sentinel data (2019), processed by ESA, CC
BY-SA 3.0 IGO)

• September 6, 2019: The
Copernicus Sentinel-2 mission takes us over a set of small towns in the
Colli Albani hills known collectively as Castelli Romani. 41)

- Located around 20 km southeast of
Rome, the Castelli Romani area is of volcanic nature, originating from
the collapsing of the Latium volcano hundreds of thousands of years
ago. The outlines of the inner and outer crater rims are clearly
visible in the image.

- Two lakes now occupy the craters,
the small Lake Nemi and the larger, oval-shaped Lake Albano. The town
of Castel Gandolfo overlooks Lake Albano and is known for its papal
summer residence where many popes have spent their summers since the
17th century.

- Owing to cooler temperatures
during summer, the hills and small towns are a popular destination for
city dwellers trying to escape the heat.

- Each town has its own attraction,
for example Ariccia is famous for its porchetta or roast pork, and
Frascati is predominantly known for its wine.

- Frascati, which is just north of
Lake Albano, is known for a number of scientific research institutes.
These include ENEA, the Italian National Agency for New Technologies,
Energy and Sustainable Economic Development; CNR, the Italian Research
Council; INFN, the National Institute for Nuclear Physics; as well as
ESA’s Earth observation center.

- From 9–13 September, ESA is
holding the φ-week event, focusing on Earth observation and
FutureEO — to review the latest developments in Open Science
trends. The week will include a variety of inspiring talks, workshops
on how Earth observation can benefit from the latest digital
technologies and help shape future missions.

Figure 18: This Sentinel-2 image was acquired on 13 October 2018, is also featured on the Earth from Space video program (image credit: ESA, the image contains modified Copernicus Sentinel data (2018), processed by ESA, CC BY-SA 3.0 IGO)

• August 21, 2019: An
unprecedented wildfire has ripped through the island of Gran Canaria,
one of Spain’s Canary Islands off the northwest coast of Africa.
The wildfire, which started on Saturday 17 August, has now started to
subside after engulfing around 10,000 hectares of land, leading to the
evacuation of over 9000 people. 42)

- The Copernicus Emergency Mapping Service was activated
to help respond to the fire. The service uses satellite observations to
help civil protection authorities and, in cases of disaster, the
international humanitarian community, respond to emergencies.

- The fire
started near the town of Tejeda and spread to Tamadaba Natural Park,
driven by a combination of high temperatures, strong winds and low
humidity. According to authorities, over 700 firefighters on the ground
and 16 aircraft helped tackle the blaze, with some flames reaching over
50 meters in height.

Figure 19: This false color
image, captured on 19 August, was created using the shortwave infrared
bands from the Copernicus Sentinel-2’s instrument, and allows us
to clearly see the fires on the ground in bright orange. Burned scars
are visible in dark brown. These bands also allow us to see through
smoke – but not through clouds (image credit: ESA, the image
contains modified Copernicus Sentinel data (2019), processed by ESA, CC
BY-SA 3.0 IGO)

• July 26,
2019: The Copernicus Sentinel-2 mission takes us over Lake Balaton in
western Hungary. With a surface area of around 600 km2 and a length of around 78 km, this freshwater lake is the largest in central Europe (Figure 20). 43)

- The lake is mainly fed by the
Zala River at its western end. The lakewater flows out near the eastern
end via an artificial channel called the Sió, which eventually
feeds into the Danube River.

- Originally five separate water
bodies, the barriers between have been eroded away to create the lake
it is today. Remnants of the dividing ridges can be seen in
Balaton’s shape – with the Tihany Peninsula on the northern
shore narrowing the width of the lake to approximately 1.5 km.

- Lake Balaton’s striking
emerald-green color in this image is most likely due to its shallow
waters and chemical composition. It is heavy in carbonates and
sulphates, and there are also around 2000 species of algae that grow in
its waters.

- The lake supports a large
population of plant and animal species. During migration and wintering
sessions, the site is an important staging area for thousands of ducks
and geese.

- Owing to its pleasant climate and
fresh water, the Lake Balaton area is a popular tourist destination.
The mountainous northern region is known for its wine, while popular
tourist towns lie on the flatter southern shore.

Figure 20: This image of Lake Balaton, captured on 27 February 2019, is also featured on the Earth from Space video program (image credit: ESA, the image contains modified Copernicus Sentinel data (2019), processed by ESA, CC BY-SA 3.0 IGO)

• July 19, 2019: The Copernicus
Sentinel-2 mission takes us over palm oil plantations in East
Kalimantan - the Indonesian part of the island Borneo. 44)

- Palm oil is the most
widely-produced tropical edible oil. It’s used in a vast array of
products – from ice cream and chocolates, to cosmetics such as
make up and soap, to biofuel. Not only is it versatile, palm oil is
also a uniquely productive crop. Harvested all year-round, oil palm
trees produce up to nine times more oil per unit area than other major
oil crops.

- To meet
global demand, palm oil trees are grown on vast industrial plantations
– leading to acres of rainforest being cut down. Between 1980 and
2014, global palm oil production increased from 4.5 million tons to 70
million tons, and is expected to increase.

- Indonesia is the largest producer
of palm oil, followed by Malaysia. Together they account for 84% of the
world’s palm oil production.

- To produce palm oil in large
enough quantities to meet growing demand, farmers clear large areas of
tropical rainforest to make room for palm plantations. This leads to a
loss of habitat for species such as the orangutan – declared as
critically endangered by the WWF. In general, burning forests to make
room for the crop is also a major source of greenhouse gas emissions.

Figure 21: In this image,
captured on 15 February 2019, the various stages of the deforestation
process are clearly visible – the green patches in the
plantations are the well-established palm oil farms, while the light
brown patches show the newly-harvested land. The surrounding lush
rainforest is visible in dark green. This image is also featured on the
Earth from Space video program (image credit: ESA, the image contains modified Copernicus Sentinel data (2019), processed by ESA, CC BY-SA 3.0 IGO)

• July 16, 2019: Celebrating 50 years since Apollo 11 blasted off with the first humans that would walk on the Moon, Copernicus Sentinel-2 captures the historic launch site at Kennedy Space Center, Cape Canaveral, Florida, US. 45)

- Just four days later on 20 July
1969, the lunar module, the Eagle, touched down. Watched on television
by millions around the world, Neil Armstrong was the first to set foot
on the Moon, famously saying, “That's one small step for man, one
giant leap for mankind.”

- A few minutes later, he was
joined by Buzz Aldrin. They took photographs, planted the US flag,
spoke to President Richard Nixon via radio transmission and spent a
couple of hours walking and collecting dust and rocks. The two men
returned to the lunar module, slept that night on the surface of the
moon, and then the Eagle began its ascent back to re-join the command
module, which had been orbiting the Moon with Michael Collins. Apollo
splashed back down safely in the Pacific Ocean on 24 July 1969.

- The Moon has again captured the attention of space agencies. ESA and international partners are now looking forward to the next era of human exploration,
and to better understand the resources available on the Moon to support
human missions longer-term. While Apollo 11 touched down for the first
time on the near side of the Moon 50 years ago, it is time to explore
the far side, examine different types of lunar rocks there to probe
deeper into the Moon’s geological history and to find resources
like water-ice that are thought to be locked up in permanently shadowed
craters near the Moon’s south pole.

Figure 22:
On 16 July 1969, the Saturn V rocket carrying Apollo 11 began its
momentous voyage to the Moon. It lifted off from launch pad 39A –
which can be seen in this Copernicus Sentinel-2 image from 29 January
2019. Launch pad 39A is the second pad down from the top (the launch
pad at the far top is 39B), image credit: ESA, the image contains
modified Copernicus Sentinel data (2019), processed by ESA, CC BY-SA
3.0 IGO

• July 12, 2019: The Copernicus
Sentinel-2 mission takes us over Mount Fuji, Japan’s highest
mountain standing at 3776 m tall. In this spring image, the mountain
can be seen coated in pure white snow. 46)

- Mount Fuji is near the Pacific
coast of central Honshu, straddling the prefectures of Yamanashi and
Shizuoka. On a clear day, the mountain can be seen from Yokohama and
Tokyo - both over 120 km drive away.

- The majestic stratovolcano is a
composite of three successive volcanoes. Generations of volcanic
activity have turned it into the Mount Fuji as we know it today. This
volcanic activity is a result of the geological process of plate
tectonics. Mount Fuji is a product of the subduction zone that
straddles Japan, with the Pacific Plate and the Philippine Plate being
subducted under the Eurasian plate.

- The last explosive activity
occurred in 1707, creating the Hoei crater – a vent visible on
the mountain’s southeast flank, as well as the volcanic ash field
which can be seen on the east side.

- Mount Fuji is a symbol of Japan,
and a popular tourist destination. Around 300,000 people climb the
mountain every year – and in the image several hiking trails can
be seen leading to the base of the mountain. The city of Fujinomiya,
visible in the bottom left of the image, is the traditional starting
point for hikers.

- Many golf courses, a popular sport in Japan, can be seen dotted around the image.

- Worshipped as a sacred mountain,
Mount Fuji is of great cultural importance for the Shinto religion.
Pilgrims have climbed the mountain for centuries and many shrines and
temples dot the landscape surrounding the volcano.

Figure 23:
This snow-capped mountain is often shrouded in cloud and fog, but this
image was captured on a clear day, by the Copernicus Sentinel-2A
satellite - flying 800 km above. This image, captured on 8 May 2019, is
also featured on the Earth from Space video program (image credit: ESA, the image contains modified Copernicus Sentinel data (2019), processed by ESA, CC BY-SA 3.0 IGO)

• July 5, 2019: The Copernicus
Sentinel-2 mission takes us over a swirl of sea ice off the east coast
of Greenland in the Irminger Sea, which is just south of the Denmark
Strait between Greenland and Iceland. 47)

- The ice (Figure 24),
which formed by freezing of the sea surface further north in the Arctic
Ocean, has drifted southwards along the coast of Greenland before
arriving at this location. The ice swirl is considered a typical eddy
or vortex, commonly found in the summer marginal ice zone off the east
coast of Greenland.

- The marginal ice zone is the
transition region from the open ocean, visible in dark blue, to the
white sea ice. Depending on wind direction, waves and ocean currents,
it can consist of small, isolated ice floes drifting over a large area
to smaller ice floes pressed together in bright white bands.

- Strong mesoscale
air—ice—ocean interactive processes drive the advance and
retreat of the sea ice edge, and result in the meanders or eddies
visible in this region.

- Investigations of such ocean
eddies and meanders began in the 1970s and 1980s in the Greenland Sea
to gain a better understanding of the interactions between the ocean,
ice and atmosphere.

Figure 24:
In this image captured on 9 June 2019, small pieces of sea ice, known
as ice floes, trace out the ocean currents beneath, resulting in a
large swirl-like feature of approximately 120 km in diameter. This
image is also featured on the Earth from Space video program (image credit: ESA, the image contains modified Copernicus Sentinel data (2019), processed by ESA, CC BY-SA 3.0 IGO)

• July 4, 2019: Mount Michael
is an active stratovolcano on the remote Saunders Island, one of the
South Sandwich Islands in the southern Atlantic Ocean. In situ
observations of the volcano prove difficult owing to its remote
location and the fact that it is almost 1000 m high and difficult to
climb. However, modern satellite imagery can help survey isolated
locations such as these. 48)

Figure 25: In these images
captured by the Copernicus Sentinel-2 mission on 29 March 2018, a
distinct hotspot can be seen in orange in the crater of the volcano.
The true-color image shows volcanic ash over the snow and smoke plumes
coming from its crater, drifting south-eastwards (image credit: ESA,
the image contains modified Copernicus Sentinel data (2018), processed
by ESA)

- The assessment of Mount Michael’s lava lake is presented in a recent report in the Journal of Volcanology and Geothermal Research.
By using modern satellites, including the US Landsat, Copernicus
Sentinel-2 and the US Terra missions, monitoring activity and thermal
anomalies within the crater is now possible.

- The paper confirms that the rare
lava lake is a continuous feature inside Mount Michael’s crater,
with a temperature of approximately 1000 °C.

- Only a handful of other volcanoes
in the world are currently hosting persistent lava lakes – Masaya
volcano, Mount Nyiragongo, Kīlauea, Mount Erebus, Mount Yasur, Ambrym
and Erta Ale.

• On 30 June 2019, a wildfire
broke out at a military training site in Lübtheen, in northern
Germany. Authorities claim it is the largest blaze in the history of
the Mecklenburg-Western Pomerania state. 49)

Figure 26: This animation was
captured by the Copernicus Sentinel-2 mission, with a resolution of up
to 10 m, on 1 July at 10:20 GMT (12:20 CEST). The true-color image
shows the smoke emerging from the training site, while the other image
was processed using the shortwave infrared which allows for a better
view of the blaze under the smoke – which can be seen in bright
orange (image credit: ESA, the image contains modified Copernicus
Sentinel data (2019), processed by ESA, CC BY-SA 3.0 IGO)

- Emergency services had
difficulties containing the site, owing to unexploded munitions from
military activities going back as far as World War II. Water has been
diverted from the Elbe river to tackle the blaze. According to local
firefighters, the fire swept through 400 hectares of forest, and
hundreds of people were evacuated from their homes.

• June 28, 2019: The Copernicus
Sentinel-2 mission takes us over the Gulf of Taranto, located on the
inner heel of southern Italy. 50)

Figure 27: Taranto, an important
coastal city, is visible on the bottom right of the image. Founded by a
Greek colony in the 8th century, the city is now an important
commercial port. The islets of San Pietro and San Paolo, known as the
Cheradi Islands, protect the Mar Grande, the main commercial port of
the city. It is separated from the Mar Piccolo, an inland lagoon, by a
cape which closes the gulf. The industrial district, which is visible
northwest of the city, has a high number of factories, oil refineries,
steelworks and iron foundries. This image, captured on 6 March 2019, is
also featured on the Earth from Space video program (image credit: ESA, the image contains modified Copernicus Sentinel data (2019), processed by ESA, CC BY-SA 3.0 IGO)

- Along the coast, the Aleppo pine
forest of the Stornara Nature Reserve is clearly visible in dark green.
It takes its name from the many starlings that migrate there during
winter. The reserve was founded in 1977 and covers an area of
approximately 1500 hectares.

- Directly above the forest, many
various patches of agricultural fields can be seen. Favored by the
Mediterranean climate, the food sector has been one of the strongest
areas of the Apulian economy. Fruit, vegetables and cereals are grown
in a range of crop types throughout the region, depending on the time
of year. The blue patches visible are greenhouses.

- Considered as the 2019 European
Capital of Culture along with Plovdiv, in Bulgaria, Matera can be seen
in the top left of the image, in the Basilicata region.

- Matera hosts an important space
hub. The Giuseppe Colombo Center for Space Geodesy, founded by the
Italian Space Agency, is located here. It sends regular laser beams to
the moon, where they reach reflectors that were placed there during the
original Apollo missions and the Lunokhod Soviet robotic missions.
These lasers measure the distance from the Earth to the moon, expanding
our knowledge of the moon’s internal structure.

- Located next
door, the Matera Space Center is one of the ground stations for the
reception and processing of data acquired by the Copernicus Sentinel
satellites for ESA.

• June 27, 2019: One of the
largest wildfires recorded in Arizona, US, has been burning since 8
June, destroying vast swathes of vegetation across the Superstition
Mountains east of Phoenix. Efforts to contain the fire include spraying
flame retardant from aircraft. Colored red so that firefighters can see
it, the retardant is dropped ahead of the path of the fire to act as a
break – and remarkably these red lines can be seen from space. 51)

Figure 28:
This Copernicus Sentinel-2 image from 24 June not only captures the
extent of the Woodbury fire and burn scars in Arizona, but also the red
lines of the retardant (image credit: ESA, the image contains modified
Copernicus Sentinel data (2019), processed by ESA, CC BY-SA 3.0 IGO)

• June 17, 2019: Today marks the 25th anniversary of World Day to Combat Desertification and Drought
(WDCD). Under its theme ‘Let’s grow the future
together,’ the initiative celebrates the 25 years of progress
made in sustainable land management. 52)

- One ambitious project – the Great Green Wall
– aims to improve life in Africa’s desert regions by
planting a belt of trees across the entire width of the continent. Once
completed, the wall will be the largest living structure on the planet
stretching across 20 countries - from Senegal in the west to Djibouti
in the east.

- By 2030, the initiative aims to
have restored 100 million hectares of degraded land, sequestered 250
million tons of carbon and created 10 million green jobs.

- Since the Green Wall started in
2007, progress has been made in restoring the Sahelian lands. In
Senegal alone, almost 12 million trees have been planted, and 25,000
hectares of degraded land restored.

- Desertification is the
degradation of dry land ecosystems, owing to overexploitation through
human activities and climate change. According to the UN, 12 million
hectares of land is lost yearly because of desertification and drought,
and 75 billion tons of fertile soil is lost due to land degradation.

Figure 29:
Captured by the Copernicus Sentinel-2 mission in 2019, this image shows
the edge of the dry desert in west Africa contrasted with vegetated
land. Signs of land degradation can be seen as brighter
“islands” around villages and to a lesser extent along
roads and rivers showing bare soil and degraded vegetation. The image
shows parts of three African countries: Senegal, The Gambia and
Guinea-Bissau (image credit: ESA, the image contains modified
Copernicus Sentinel data (2019), processed by ESA, CC BY-SA 3.0 IGO)

• June 14, 2019: The Copernicus
Sentinel-2 mission takes us over the island of Bali, one of the 27
provinces of Indonesia. - Indonesia has more volcanoes than any other
country in the world, owing to its position on the Pacific Ring of
Fire. The islands of Java, Lombok, Sumbawa and Bali lie over a
subduction zone where the Indo-Australian plate slides under the
Eurasian plate, creating frequent seismic activity. 53)

- The central volcano, which is a
predominant feature in this image, is called Mount Agung or Gunung
Agung, meaning ‘Great Mountain’. The symmetrical and
conical stratovolcano is the highest in Bali, standing at over 3000 m.
When it erupted in 1964, it was one of the largest eruptions of the
20th century, claiming over 1000 lives and leaving more than 80,000
people homeless.

- After being dormant over the
following 50 years, Agung reawakened in November 2017. Fortunately,
small earthquakes warned authorities in time for 100,000 people to be
evacuated to safety. Agung still remains very active, with frequent
small eruptions spewing ash and lava, causing flights to be cancelled.

- In the image of Figure 30, a bright orange spot can be seen in the volcano’s crater. Recent research
provides evidence that Agung and its neighboring Batur volcano, visible
northwest of Agung, may have a connected magma plumbing system. 54)

- Mount Batur, or Gunung Batur, has an unusual shape, with the volcanic cone visible in the center of two concentric calderas.

Figure 30:
Dotted with clouds, Mount Seraya is visible on the peninsula that juts
to the east. Its volcanic rock creates a rugged terrain, but is
surrounded by lush vegetation. The area is well known for its many
Hindu temples, including the famous Lempuyang Temple, known locally as
Pura Luhur Lempuyang. This image of Sentinel-2, captured on 2 July
2018, is also featured on the Earth from Space video program (image credit: ESA, the image contains modified Copernicus Sentinel data (2018), processed by ESA, CC BY-SA 3.0 IGO)

• June 7, 2019: The Copernicus
Sentinel-2 mission takes us over Lake Valencia, in northern Venezuela.
This false-color image (Figure 31) was
processed in a way that makes vegetation of the Henri Pittier National
Park, north of the lake, appear in fluorescent green. These bright
colors contrast with the blackness of the lake. 55)

- Unfortunately, the inflow of
untreated wastewater from the surrounding industrial and agricultural
lands has led to the lake to become contaminated. The lake now suffers
from algal blooms and between 1960 and 1990 it lost over 60% of its
native fish species.

- It was at this very lake that the
German naturalist and explorer, Alexander von Humboldt, witnessed how
human behavior could cause harm to our natural ecosystem and climate.
During his travels in the late 18th century, he noted the surrounding
barren land which had been cleared for plantations and crops for sugar
and tobacco. He attributed the decreasing water levels in the lake to
climate change.

- “When forests are destroyed, the springs are entirely dried up,” he wrote in his travel report, the Relation historique du voyage aux régions équinoxiales du nouveau continent (1814-17).
“The beds of the rivers are converted into torrents whenever
great rains fall on the heights.... Hence it results, that the
destruction of forests, the want of permanent springs, and the
existence of torrents, are three phenomena closely connected
together.”

- The now poor-quality waters of Lake Valencia prevent the development of tourism and recreational activities in the region.

Figure 31: With a surface area of 370 km2,
Lake Valencia formed a few million years ago and is now a reservoir for
the cities of Valencia on the west shores and Maracay on the east
shores. This image, which was captured on 2 February 2019 with
Sentinel-2, is also featured on the Earth from Space video program (image credit: ESA, the image contains modified Copernicus Sentinel data (2019), processed by ESA, CC BY-SA 3.0 IGO)

• May 31,2019: The Copernicus
Sentinel-2 mission takes us over El Salvador, the smallest and most
densely populated country in Central America. 56)

- Lake Guija, visible in the top left of the image (Figure 32),
lies on the border between El Salvador and Guatemala. The lake once
formed part of the Mayan Empire and legend says that it also hides an
ancient city beneath its waters.

- El Salvador sits on the eastern
edge of the Pacific Ring of Fire, and despite being a small country, it
has 25 volcanoes. The volcano complex of the Cerro Verde National Park
can be seen dotted with clouds in the lower left of the image.

Figure 32:
Captured on 30 January 2019, this false-color image was processed in a
way that makes vegetation appear red. This image is also featured on
the Earth from Space video program (image credit: ESA, the image contains modified Copernicus Sentinel data (2019), processed by ESA, CC BY-SA 3.0 IGO)

- The Cerro Verde National Park is
over 2000 m above sea level. It is home to a cluster of three volcanoes
surrounded by lush rainforest. Santa Ana, the highest volcano in the
country, is clearly visible with its circular peak.

- Izalco, located directly below
Santa Ana, was born in 1770 and has erupted more than 50 times since.
Its odd color and shape is due to these frequent eruptions.

- The large body of water to the
right of Izalco is Lake Coatepeque, one of the largest crater lakes in
the country. It is home to a variety of aquatic life and has remnants
of ancient volcanic activity such as hot springs and openings emitting
steam known as fumaroles.

- The large volcano in the right of
the image is named San Salvador. It is adjacent to the capital, with
which it shares its name. The city sprawls close to the nearby Lake
Ilopango, which occupies the crater of an extinct volcano.

• May 24, 2019: The image of Figure 33
depicts the fragmented coast of western Pakistan, part of the Indus
River Delta. A river delta forms when sediment carried from the river
enters a stagnant body of water, creating an alluvial fan, which in
this case extends 150 km along the coastline. The Indus River, visible
on the right, veers through the Sindh Province and is one of the
longest rivers in the world, rising in Tibet and flowing around 3000 km
before emptying into the Arabian Sea. 57)

- The Indus Delta consists of creeks, swamps, marshes and the seventh largest mangrove forest in the world.

- However, owing to major
irrigation works and dams built on the river, as well as low rainfall,
the amount of silt discharged into the sea has reduced, affecting the
mangrove and local community significantly. A huge proportion of the
delta has been lost and the survival of the delta freshwater species,
including the Indus river dolphin, are at risk.

- Also responsible for pollution is the port city of Karachi, which is partially visible in the top left of the image.

- To the top right, there are two
important bodies of water on the edge of the stony desert, both of
which are also wildlife sanctuaries. The artificial, square-shaped
Haleji Lake, was expanded in World War II, for the use of additional
water for the troops. The freshwater lake supports an abundance of
aquatic vegetation, and is home to a number of species of birds.

- To the far right, the freshwater
Keenjhar Lake is a major source of drinking water for Karachi, as well
as for Thatta, which is to the right of the yellow-beige patch of land.

- Both lakes, as well as the River Indus Delta, are sites of wetland designated to be of international importance under the Ramsar Convention – an international treaty for the conservation and sustainable use of wetlands.

Figure 33:
Captured on 14 April 2018 by the Copernicus Sentinel-2A satellite, this
image shows western Pakistan and an important wetland area. This image
is also featured on the Earth from Space video program (image credit: ESA, the image contains modified Copernicus Sentinel data (2018), processed by ESA, CC BY-SA 3.0 IGO)

• May 17, 2019: The Copernicus
Sentinel-2 satellite takes us over the Po Valley in northern Italy. The
Po River, the longest river in Italy, flows over 650 km from west to
east across the country, and ends at a delta projecting into the
Adriatic Sea near Venice. The river flows through some of Italy’s
important cities of the north. 58)

Figure 34: Image of the Po
Valley, the most densely populated area in Italy, accounting for nearly
half of the national population. This composite image contains several
images captured between June 2018 and February 2019, allowing us to see
the area free from clouds and smog. This image is also featured on the Earth from Space video program (image credit: ESA, the image contains modified Copernicus Sentinel data (2018–19), processed by ESA, CC BY-SA 3.0 IGO)

- On the very left of the image,
next to the river, the city of Turin can be seen. A business and
cultural center, Turin is the capital of the Piedmont region. Rich in
history, the city is home of the Shroud of Turin, a famous religious
relic, as well as the Residences of the Royal House of Savoy. Turning
to modern day, several International Space Station modules, such as
Harmony and Columbus, were manufactured in Turin.

- Moving east, the city of Milan
can be seen nestling below the Alps. Although Milan is the second most
populous city in Italy after Rome, the wider metropolitan area extends
over Lombardy and eastern Piedmont, making it the largest metropolitan
area in Italy.

- Further east, the blue body of Lake Garda can be seen to the left of Verona. With an area of 370 km2,
Garda is the largest lake in Italy and the third largest in the Alpine
region. East of the lake is the Adige River, flowing south before
curving east toward Verona. The city of Verona has been awarded World
Heritage Site status by UNESCO because of its urban structure and
architecture such as the circular Roman amphitheater.

- Along the coast, the turquoise
colors of the Venetian lagoon and the islands that make up the city of
Venice are visible. Famous for its musical and artistic cultural
heritage, millions of tourists flock to the archipelago every year.

- As the Po River nears the
Adriatic Sea, its agricultural landscape dominated by fields can be
seen. Agriculture is one of the main industries in the Po Basin because
of the fertile soils. Cereals, including rice, and a variety of
vegetables are commonly grown in this area.

- The main arms of the river push
the delta into the sea. An important ecosystem, the area has been a
regional park since 1988 and a biosphere reserve since 2015.

• May 10, 2019: ESA's Living
Planet Symposium – the largest Earth observation conference in
the world – is being held on 13–17 May in Milan, Italy.
Held every three years, these symposia draw thousands of scientists and
data users from around the world to discuss their latest findings on
how satellites are taking the pulse of our planet. 59)

- Over 4000 participants will
gather at the largest congress center in Europe: the MiCo Convention
Center. With its iconic architecture, this modern building has become a
landmark. The event will not only see scientists present their latest
findings on Earth’s environment and climate derived from
satellite data, but will also focus on Earth observation’s role
in building a sustainable future and a resilient society.

- Milan is the second biggest city
in Italy and, like most large urban environments, it suffers from air
pollution. While there is an effort to reduce the emission of
pollutants, the city is also incorporating more vegetation into its
development plans. This not only makes the environment more pleasant,
but the plants also help soak up greenhouse gases such as carbon
dioxide.

- The Bosco
Verticale, or the Vertical Forest, for example, aims to inspire the
need for urban biodiversity. The two tower blocks have plants and trees
planted on its façade, and are located just north of the
historical center. The vegetation covering both towers is equivalent to
20,000 m2 of forest and home to a variety of birds and
butterflies. This vegetation absorbs approximately 30 tons of carbon
dioxide per year.

- Another example of the
city’s efforts to ‘go green’, is the Biblioteca degli
Alberi, or Library of Trees, visible next to the Bosco Verticale. With
its geometric design and irregular patches of land, the gardens are
home to over 100,000 plants and trees, interlinked with pedestrian and
bike paths.

- But it doesn’t stop there, the local government aims to plant another three million trees by 2030.

Figure 35: In this
high-resolution image, captured by Copernicus Sentinel-2 orbiting
around 800 km above, the center of Milan is clearly visible. The famous
Milan Cathedral or Duomo di Milano with its surrounding square can be
seen in the center of the image. Taking six centuries to complete, it
is one of the largest gothic cathedrals in the world. This image, also
featured on the Earth from Space video program,
was captured on 24 September 2018 by the Copernicus Sentinel-2 mission.
(image credit: ESA, the image contains modified Copernicus Sentinel
data (2018), processed by ESA, CC BY-SA 3.0 IGO)

• May 03,
2019: The Copernicus Sentinel-2 mission takes us over an area in
southern Germany, where approximately 15 million years ago an asteroid
crashed through Earth’s atmosphere. The high-speed impact formed
what is now known as the Ries crater. Although difficult to spot at
first in the image, the result of the impact is actually still visible
today. 60)

- With a diameter of 26 km, the rim
of the crater can be seen as a semi-circle in the image, delineated by
dark green forest to the south. The flat ‘crater floor’ is
ideally suited for agricultural use and the corresponding fields mark
the crater’s extent.

- The medieval town of
Nördlingen (in the Donau-Ries district of Bavaria) was built in
its depression. The historical center, approximately 1 km wide, appears
as a reddish circle, visible with its red rooftops surrounded by a
wall.

- The asteroid was estimated to be
travelling at 70,000 km per hour, and when it made impact with Earth,
the high-speed force exposed the rock to intense pressure and heat,
over 25,000°C. The impact led to the creation of over 70,000 tons
of microscopic diamonds, each around 0.2 mm in size.

- Overlooked by the town’s
inhabitants, the stone buildings were constructed almost entirely with
diamond-encrusted rock. Details on the impact can be found in the
well-known Rieskrater Museum in Nördlingen.

- For centuries, Nördlingen
locals believed the town was built in the crater of a volcano. But in
the 1960s two American scientists (Gene Shoemaker and Edward Chao)
proved that the depression was, in fact, caused by a meteorite impact.
Today, visitors around the world gather to marvel at this glittering
town, also known as the backdrop to the original Willy Wonka and the
Chocolate Factory film.

Figure 36:
The Sentinel-2 satellite of ESA captured this image of the
Nördlinger Ries on 1 July 2018, it is also featured on the Earth from Space video program (image credit: ESA, the image contains modified Copernicus Sentinel data (2018), processed by ESA, CC BY-SA 3.0 IGO)

Figure 37: An aerial view of the town of Nördlingen inside the meteorite Ries crater

• April 26, 2019: The
Copernicus Sentinel-2 mission takes us over Australia’s northeast
state of Queensland, where a large amount of sediment is visible
gushing into the Coral Sea, close to the Great Barrier Reef lagoon. 61)

- In early 2019, many areas in
Queensland received more than their annual rainfall in less than a
week. The downpour led to millions of dollars’ worth of damage,
including homes being destroyed and the loss of almost 500,000 cattle.

- The Burdekin River rises on the
northern slopes of Boulder Mountain and flows close to 900 km before
emptying into the Coral Sea. The Burdekin River is one of Australia's
larger rivers by discharge volume, and is a major contributor of
sediment and freshwater to the Great Barrier Reef lagoon.

- The Great Barrier Reef, the
world’s largest coral reef, extends for 2000 km along the
northeast coast of Australia and covers almost 350,000 km2.
The reef is an interlinked system of about 3000 reefs and 900 coral
islands, divided by narrow passages. An important area of biodiversity,
the reef was made a UNESCO World Heritage Site in 1981.

- The
sand-color sediment plume can be seen stretching over 35 km from the
coast, dangerously close to the vivid turquoise reef. The blues of the
coral contrast with the dark-colored waters of the Coral Sea.

- The coral reef suffers regular
damage, more than half of the reef has disappeared over the last 30
years owing to climate change, coral bleaching and pollution. Large
quantities of sediment that flow out from rivers carry chemicals and
fertilizers from inland farms. The sediment blankets the coral, and
reduces the amount of light, as well as potentially causing harmful
algae blooms.

- Data from Copernicus Sentinel-2
plays a key role in providing information on pollution in lakes and
coastal waters. Frequent coverage is also fundamental to monitoring
floods.

Figure 38: This image was
captured a few days after the torrential rain, and shows the muddy
waters flowing from the Burdekin River into the Coral Sea. It was
captured on 10 February 2019, it is also featured on the Earth from Space video program (image credit: ESA, the image contains modified Copernicus Sentinel data (2019), processed by ESA, CC BY-SA 3.0 IGO)

• April 19, 2019: The
Copernicus Sentinel-2 mission takes us over one of the most remote
islands in the world: Easter Island. Located in the Pacific Ocean, over
3500 km off the west coast of South America, this Chilean island is
also known as Rapa Nui by its original inhabitants. The island was
given its current name the day when the Dutch navigator Jacob Roggeveen
arrived on 5 April 1722 – on Easter Sunday.

Figure 39: Easter Island, with a size of 163.6 km2
and a population of 7500, is a Chilean island in the southeastern
Pacific Ocean, at the south-easternmost point of the Polynesian
Triangle in Oceania. A Sentinel-2 acquired this image on 7 April 2019,
it is also featured on the Earth from Space video program (image credit: ESA, the image contains modified Copernicus Sentinel data (2019), processed by ESA, CC BY-SA 3.0 IGO)

- The island is famous for its
monolithic stone statues, called Moai, said to honor the memory of the
inhabitants’ ancestors. There are nearly 1000 scattered around
the island, usually positioned near freshwater. Many are located near
the Rano Raraku volcano, on the southeast coast. The white edges along
the southern coast show the harsh waves colliding with the shore.

- An interesting feature of the
image is the ochre-orange color of the Poike – the peninsula on
the eastern end of the island. In ancient times, it is said that there
was a lot of vegetation on the island. However, land clearing for
cultivation and the Polynesian rat played a role in deforestation,
leading to the erosion of the soil, particularly in the east.

- Several reforestation projects
have been attempted, including a eucalyptus plantation in the middle of
the island, visible in dark green. The brown patch to the right of the
plantation is likely to be a burn scar from a wildfire.

- The majority of the
island’s inhabitants live in Hanga Roa, the main town and harbor
on the west coast, clearly visible in the image. Interestingly, the
long runway of the island’s only airport was once designated as
an emergency landing site for the US space shuttle.

- At the very edge of the southwest
tip of the island lies Ranu Kao, the largest volcano on the island. Its
shape is distinctive owing to its crater lake, one of the
island’s only three natural bodies of water.

- Many
tourists are drawn to the island for its mysterious history and
isolated position. What is relatively unknown is the existence of two
small beaches on the northeast coast. Anakena beach has white, coral
sand, while the smaller Ovahe beach, surrounded by cliffs, has pink
sand.

• April 5, 2019: This week,
ESA is focusing on its core Basic Activities, which, for Earth
observation, include preserving precious data. Long-time series of
datasets are needed to determine changes in our planet’s climate
so it is vital that satellite data and other Earth science data are
preserved for future generations and are still accessible and usable
after many years. This example includes a series of satellite images
going back to 1998. 62)63)64)

Figure 40: This long-time series
of over 150 images, captured by the US Landsat series and the
Copernicus Sentinel-2 missions, shows the development over 21 years of
an important land reclamation project in the Western Desert of Egypt.
This comparison highlights how this agricultural project has developed
between January 1998 and March 2019. These images are also featured on
the Earth from Space video program (image credit: USGS/contains modified Copernicus Sentinel data (2019), processed by ESA, CC BY-SA 3.0 IGO)

- Egypt is over 95% desert, making
a very small proportion of its land suitable for agriculture. As the
demand for food grows, the need for agricultural development in desert
areas has intensified.

- This set of images shows an important land reclamation project in East Oweinat, in the Western Desert of Egypt.

- The circular shapes in the
images, each approximately 800 meters wide, indicate the irrigation
method used here, with water being supplied by a set of sprinklers
rotating around a central pivot. Fossil water, stored underground for
thousands of years, comes from the Nubian Sandstone Aquifer, the largest known fossil aquifer discovered.

- The water in the East Oweinat
area is low in salt content, making it ideal for cultivation purposes.
Crops such as wheat, potatoes and barley are grown here, and are
exported through the Sharq El Owainat airport, visible in the right
side of the image.

- Another interesting feature in
this time series is the drifting sand dunes visible mainly in the upper
left corner, which is a phenomena common in sandy deserts with constant
winds.

- Changes over the last 21 years
are clearly visible when more fields develop, but the data also show
other subtle changes within the fields themselves. This data can be
used to monitor changes in land-cover over time. Long-term preservation
of the satellite data from different missions ensures that changes to
the land can be monitored by analyzing data from the archives.

• March 22, 2019: Today is
World Water Day, but with millions of people in Mozambique, Malawi and
Zimbabwe struggling to cope in the aftermath of Cyclone Idai, the
notion of water shortages may not be at the forefront of our minds
right now. Even so, floods, like we see here, lead to real problems
accessing clean water. Whether the problem is inundation or water
scarcity, satellites can help monitor this precious resource. 65)

Figure 41: Water levels in the
Theewaterskloof Dam in South Africa’s Western Cape Province have
dropped dramatically over recent years. The dam is the major source of
water for domestic and agricultural uses in the region. Over the last
year, this lack of water has caused the production of grain to drop by
more than 36% and the production of wine grapes to drop by 20%, for
example. It is estimated that it will need to receive at least three
years of good winter rainfall for it to return to its earlier healthy
level. Thanks to the TIGER initiative, the Stellenbosch University is
applying machine-learning algorithms to data from the Copernicus
Sentinel-1 and Sentinel-2 missions to carefully monitor the situation
(video credit: ESA, the video contains modified Copernicus Sentinel
data (2017–18), processed by ESA, CC BY-SA 3.0 IGO)

- With more than two billion people
living without safe water and around four billion people suffering
severe water scarcity for a least one month a year, achieving water for
all is a huge challenge. And, coupled with a growing global population
and climate change, it’s likely to become even more challenging.

- Water allows life on Earth to
thrive. The same water has existed for billions of years, cycling
through the air, oceans, lakes, rocks, animals and plants and back
again. The water we drink today may have once been inside a dinosaur!

- Our most precious resource is
probably the strangest thing in the universe. Defying the laws of
chemistry, it’s the only known substance that can exist naturally
as a gas, liquid and solid within a relatively small range of air
temperatures and pressures found on the surface of Earth.

- Although there is no shortage of
water on Earth, less than 3% is freshwater. Then the vast majority of
this is locked up in icecaps and glaciers, leaving less than 1%
available for drinking and other domestic needs, agriculture and
industrial processes, and more.

- Freshwater
is the single most important natural resource on the planet, but we are
very rapidly running out of it – as illustrated by dwindling
water bodies.

Figure 42:
The Earth's water cycle. The total amount of water present on the Earth
is fixed and does not change. Powered by the Sun, water is continually
being circulated between the oceans, the atmosphere and the land. This
circulation and conservation of the Earth's water, known as the water
cycle, is a crucial component of our weather and climate (image credit:
ESA/AOES Medialab)

Figure 43: Glacial decline (10 December 2018).66)
A paper published recently in Nature Geosciences describes how a
multitude of satellite images have been used to reveal that there has
actually been a slowdown in the rate at which glaciers slide down the
high mountains of Asia. This animation simply shows how glaciers in
Sikkim in northeast India have changed between 2000 and 2018. One of
the images is from the NASA/USGS Landsat-7 mission captured on 26
December 2000 and the other is from Europe’s Copernicus
Sentinel-2A satellite captured on 6 December 2018 [image credit:
NASA/USGS/University of Edinburgh/ETH Zurich/ the image contains
modified Copernicus Sentinel data (2018)]

• March 22, 2019: The 22 March is World Water Day,
which focuses on the importance of freshwater. The Sustainable
Development Goals of the United Nations aim to achieve a better and
more sustainable future. Goal number 6 focuses on ensuring the
availability and sustainable management of water for all by 2030. This
image takes us over Lake Chad at the southern edge of the Sahara, where
water supplies are dwindling. 67)

- Once one of Africa’s
largest lakes, Lake Chad has shrunk by around 90% since the 1960s. This
receding water is down to a reduction of precipitation, induced by
climate change, as well as development of modern irrigation systems for
agriculture and the increasing human demand for freshwater.

Figure 44: This comparison shows
Lake Chad imaged on 6 November 1984 by the US Landsat-5 satellite and
on 31 October 2018 by the Copernicus Sentinel-2A satellite. The rapid
decline of the lake’s waters in just 34 years is clearly to see.
These images are also featured on the Earth from Space video program
(image credit: ESA, the image contains modified Copernicus Sentinel
data (2018), processed by ESA (For Landsat image: USGS/ESA), CC BY-SA
3.0 IGO)

- Straddling the border of Chad,
Niger, Cameroon and Nigeria, the lake is a major source of freshwater
for millions of people in the area. It is also a source for irrigation,
fishing and it was once rich in biodiversity.

- As the lake continues to dry up,
many farmers and herders move towards greener areas or move to larger
cities to seek alternative work. Several attempts have been made to
replenish these shrinking waters, however little progress has been
achieved.

- The borders of the lake’s
body are only partly visible in the most-recent image – as the
majority of the shoreline is swamp and marsh. The Chari River, visible
snaking its way towards Lake Chad at the bottom of the image, provides
over 90% of the lake’s waters. It flows from the Central African
Republic following the Cameroon border from N'Djamena, where it joins
with its main tributary the Logone River.

- The demand for water is growing
inexorably. Access to water is vital – not only for drinking, but
also for agriculture, energy and sanitation. By providing measurements
of water quality and detecting changes, the Copernicus Sentinel-2
mission can support the sustainable management of water resources.

• March 22, 2019:World Water Day!68)
The 66th United Nations General Assembly adopted a resolution declaring
the Water Action Decade from 22 March 2018 to March 2028. The UN Water
Action Decade is pursuing two goals:

- Spreading knowledge on the topic
of water and water pollution control, including information on
water-related Sustainable Development Goals (SDGs);

Figure 45: The UN Sustainable
Goal 6 is crystal clear: Water for all by 2030. For World Water Day we
take a look at ways that space can help this global challenge. While
Earth-observing satellites monitor our precious water resources,
technologies developed for human space missions also serve global needs
in harsh environments here on Earth (video credit: ESA)

• March 21, 2019: The UN International Day of Forests is held annually on 21 March.
It raises awareness of the importance of all types of forest and the
vital role they play in some of the biggest challenges we face today,
such as addressing climate change, eliminating hunger and keeping urban
and rural communities sustainable. As the global population is expected
to climb to 8.5 billion by 2030, forests are more important than ever. 69)

- This year,
the International Day of Forests put a particular focus on education,
but also on making cities a greener, healthier and happier place to
live. In cities, trees can help many urban challenges. They act as air
filters by removing pollutants, reduce noise pollution, offer shade and
provide an oasis of calm in an otherwise busy urban environment, for
example.

- While Bangkok, which is home to
over eight million people, is an example of ongoing efforts being made
to increase green spaces to improve city life, it also has a
much-valued green haven, which can be seen in the center of the image.

- This horseshoe or lung-shaped, green oasis is Bang Kachao and is in the middle of the bustling city.

- Rich in gardens, mangroves and
agricultural fields, the 2000 hectares of land is a significant
contrast to the vastness of the city’s urban sprawl. Fighting
Bangkok’s traffic and air pollution, Bang Kachao’s lush
green forest provides the dense city, and the surrounding Samutprakan
province, with a flow of fresh air.

Figure 46:
Captured on 22 January 2019 by the Copernicus Sentinel-2B satellite,
this true-color image shows Thailand’s most populous city
Bangkok, and its ‘Green Lung’ Bang Kachao. The
government-protected oasis of green is wrapped around the Chao Phraya
River, which is seen flowing through the city of Bangkok before
emptying into the Gulf of Thailand (image credit: ESA, the image
contains modified Copernicus Sentinel data (2019), processed by ESA, CC
BY-SA 3.0 IGO)

Legend to Figure 46:
Bang Kachao is an artificial island formed by a bend in the Chao Phraya
River and a canal at its western end. It lies south of the Thai capital
Bangkok in the Phra Pradaeng District of Samut Prakan Province. The
island, covering 16 km2, has been traditionally agricultural with only a relatively small population.

• March 21, 2019: Billions of
image pixels recorded by the Copernicus Sentinel-2 mission have been
used to generate a high-resolution map of land-cover dynamics across
Earth’s landmasses. This map also depicts the month of the peak
of vegetation and gives new insight into land productivity. 70)

- Using three
years’ worth of optical data, the map can indicate the time of
vegetation peak and variability of vegetation across seasons. Developed
by GeoVille, an Austrian company specialized in the analysis of
satellite data, this land-cover map dynamics map uses Copernicus
Sentinel-2 archive data from 2015-18, and gives a complete picture of
variations of vegetation. The map is displayed at a resolution of 20 m,
however a 10 m version is available on request.

Figure 47: Data from the
Copernicus Sentinel-2 mission has been used to generate a new
high-resolution map of vegetation across Earth’s entire landmass.
The new map depicts global vegetation dynamics and gives insight into
land productivity. The time of vegetation peak i.e. the month at which
greenness maximum occurs is shown in red (spring) and green (summer) to
blue tones (autumn and winter.) The variability of vegetation greenness
is represented by light tones in low amplitude areas such as managed
grasslands, while high amplitudes are represented by saturated color
tones. Areas with low biomass such as urban areas and open bodies of
water are shown in black, while areas with higher biomass appear in
grey and white tones (image credit: ESA, the image contains modified
Copernicus Sentinel data (2016–18), processed by GeoVille)

- It can, for example, support
experts working with land-cover classification and can serve as input
for services in areas such as agriculture, forestry and
land-degradation assessments.

- “In particular, we use this
as a basis to develop services for the agrofood industry and farmers
growing potatoes and other crops, as well as information on how
vegetation changes over the year,” explains Eva Haas, Head of
GeoVille’s Agricultural Unit (Innsbruck, Austria).

Figure 48:
The inland delta of the Niger River spreads across central Mali –
a unique ecosystem in West Africa. A result of the Niger river flowing
into the sandy Sahelian plains, this vast network of channels, swamps,
and lakes mitigates the severity of the arid climate by supplying water
during October and November (blue). In contrast the image shows the
sparse rain fed vegetation in the surrounding region (dark green). This
image is part of a new high-resolution map of vegetation across
Earth’s entire landmasses generated with Copernicus Sentinel-2
data (image credit: ESA, the image contains modified Copernicus
Sentinel data (2016–18), processed by GeoVille)

- The land-cover dynamic layer was
produced with GeoVille’s processing engine LandMonitoring.Earth,
a fully-automated land-monitoring system built on data streams from the
Copernicus Sentinel-1 and Sentinel-2 missions, as well as ESA third
party missions such as the US Landsat missions.

- “Using the system, we
processed the complete Copernicus Sentinel-2 image archive along with
artificial intelligence, machine learning and big data
analytics,” explains Michael Riffler, Head of Research and
Development at GeoVille.

- “However, the key is the
dense time-series of the Copernicus Sentinel-2 data which allows this
information to be retrieved for the first time. To date, we have
processed more than 23 billion pixels.”

Figure 49:
The image shows different crop types around Emmelrod in the
Netherlands. Here, green shows summer crops, red is potatoes, orange is
market crops, yellow is cereals and blue depicts grassland. The area is
important for the agrofood sector and, in particular, has strong ties
to the international potato industry. By integrating Copernicus
Sentinel-2 based crop-type monitoring directly into existing industry
workflows, the agrofood industry can gain information about the growth
and potential yield of crops, potatoes in particular, including the
impact of ongoing droughts (image credit: ESA, the image contains
modified Copernicus Sentinel data (2018), processed by GeoVille)

- The development has been done
through ESA’s Earth observation innovation hub – Φ-lab,
and has been implemented by GeoVille and its subsidiary in the
Netherlands – GEO4A.

- “This map forms an
excellent foundation for other – more specialized – land
cover classifications, whose development and deployment can be further
accelerated by applying machine learning and AI,” says Iarla
Kilbane-Dawe, the head of ESA’s Φ-Lab in Frascati, Italy.

- The LandMonitoring.Earth system
is designed to efficiently implement major client solutions such as the
European Copernicus Land Monitoring Service products. Experts can
specify desired land monitoring data for any place on the globe for any
given time period, and receive a quality-controlled output, depending
on the required geographic coverage and frequency.

- The idea is to make information available to non-experts along with the specific resources and tools that they need.

Sentinel-2 Continued

• March 15, 2019: The
Copernicus Sentinel-2 mission takes us over Nairobi, one of the fastest
growing cities in East Africa. 71)

- The population of Nairobi has
increased significantly in the last 30 years, with rural residents
flocking to the city in search of employment. The city, visible in the
center of the image, now has a population of over three million, with
the vast majority spread over 200 informal settlements.

- Kibera, which can be seen as a
light-colored patch at the south-western edge of the city, is
considered one of the largest urban slums in Nairobi. Most residents
live in small mud shacks with poor sanitation, a lack of electricity
and limited access to clean water.

- While migration provides economic
benefits to the city, it also creates environmental challenges. Owing
to its urbanization, the city has spread into green spaces such as the
nearby parks and forests. In this image, the densely populated area is
contrasted with the flat plains of Nairobi National Park, directly
south of the city. The 117 km2 of wide-open grass plains is
colored in light-brown. The park is home to lions, leopards, cheetahs
and has a black rhino sanctuary.

- The dark patches in the image are
forests. The Ngong Forest, to the west of the city, includes exotic and
indigenous trees, and hosts a variety of wild animals including wild
pigs, porcupines, and dik-diks.

- To the north of the city, the
dark Karura Forest is visible. The 1000 hectare urban forest features a
15 m waterfall, and hosts a variety of animals including bush pigs,
bushbucks, suni and harvey’s duiker, as well as some 200 bird
species.

- Although Africa is responsible
for less than 5% of global greenhouse-gas emissions, the majority of
the continent is directly impacted by climate change. Rapid population
growth and urbanization also exposes residents to climate risks.

- On 14 March 2019, the first regional edition of the One Planet Summit took place at the UN Compound, which is in the north of the city. The One Planet Summit, part of the UN Environment Assembly, focuses on protecting biodiversity, promoting renewable energies and fostering resilience and adaptation to climate change.

- Data from Copernicus Sentinel-2
can help monitor changes in urban expansion and land-cover change.
Copernicus Sentinel-2 is a two-satellite mission. Each satellite
carries a high-resolution camera that images Earth’s surface in
13 spectral bands.

- As delegates gather in Nairobi
for the UN Environment Assembly, ESA is saddened by the news of the
Ethiopian Airlines accident. Lives lost included those working for
organizations also dedicated to achieving a better world for all and
who were travelling to the assembly. — Our thoughts are with the
families, colleagues and friends of those affected.

• February 25, 2019: This Copernicus Sentinel-2 image of Figure51 shows a huge plume of sediment gushing into the sea following heavy rainfall in the Rome area. 72)

- The Tiber River can be seen
snaking its way southwards in the image. The third longest river in
Italy, it rises in the Apennine Mountains and flows around 400 km
before flowing through the city of Rome and draining into the sea near
the town of Ostia. The Tiber River plays an important role in sediment
transport, so coastal waters here are often discolored. However, the
recent rains resulted in a large amount of sediment pouring into the
Tyrrhenian Sea, as this image shows. The sediment plume can be seen
stretching 28 km from the coast, carried northwest by currents.

Figure 51:
The Copernicus Sentinel-2B satellite captured this true-color image on
5 February 2019, just three days after heavy rainfall in Rome and the
surrounding area of Lazio, Italy. It shows sediment gushing into the
Tyrrhenian Sea, part of the Mediterranean Sea. The downpour on 2
February led to flooded streets, the closing of the banks of the Tiber
River and several roads (image credit: ESA, the image contains modified
Copernicus Sentinel data (2019), processed by ESA, CC BY-SA 3.0 IGO)

• February 22, 2019: The
Copernicus Sentinel-2A satellite takes us over western Sicily and the
islands of Favignana and Levanzo in Italy. The image of Figure 52
shows a false-color image included the near-infrared channel and was
processed in a way, that makes vegetation appear in bright red. 73)

- The bright turquoise colors, near
the port city of Trapani, at the top of the image, and the Isola Grande
in the middle of the image, depict salt marshes. Both the Saline di
Trapani e Paceco Nature Reserve and the Stagnone Nature Reserve with
their shallow sea waters, windy coast and abundant sunshine, make the
area between Marsala, at the bottom of the image, and Trapani an ideal
place for salt production.

- The reserve consists of more than
1000 hectares of landscape dotted with windmills, migratory birds such
as flamingos and light-red lagoons visible in summer. This
greenish-blue color is heavily contrasted with the black of the open
Mediterranean Sea.

- The islands, off the coast, are
rich in history, both boasting Paleolithic and Neolithic cave
paintings. The most famous being the Grotta del Genovese on the
picturesque island of Levanzo, at the top left of the image. The cave
was discovered only in 1949 and is estimated to be between 6000 and 10
000 years old.

- Below, the butterfly-shaped
island of Favignana, known for its tuna fisheries and a type of
limestone known as tufa rock, is the largest of the Aegadian islands.
In 241 BC, one of the Punic Wars’ naval battles was fought at the
Cala Rossa (Red Cove), named after the bloodshed.

Figure 52:
Captured on 3 September 2018 by the Copernicus Sentinel-2A satellite,
this false-color image shows part of western Sicily in Italy and two of
the main Aegadian Islands: Favignana and Levanzo. This image is also
featured on the Earth from Space video program (image credit: ESA, the image contains modified Copernicus Sentinel data (2018), processed by ESA, CC BY-SA 3.0 IGO)

• February 15, 2019:
Copernicus Sentinel-2 brings you some of the jewels of the Maldives for
Valentine’s week. Arguably one of the most romantic destinations
in the world, the Maldives lie in the Indian Ocean about 700 km
southwest of Sri Lanka. The nation is made up of more than 1000 coral
islands spread across more than 20 ring-shaped atolls. 74)

- Like many
low-lying islands, the Maldives are particularly vulnerable to
sea-level rise. In fact, the Maldives are reported to be the flattest
country on Earth, with no ground higher than 3 m and 80% of the land
lying below 1 m. With satellite records showing that over the past five
years, the global ocean has risen, on average, 4.8 mm a year, rising
seas are a real threat to these island jewels.

- With the promise of white sandy
beaches, azure ocean waters and coral reefs, this romantic getaway
draws more than 600,000 tourists every year. While tourism is extremely
important for the national economy, development on these pristine
islands create pressures, such as ensuring an adequate supply of
freshwater, treating sewage and potential pollution entering the ocean.
Other environmental issues facing the Maldives include the loss of
habitats of endangered species and the damage to the coral reefs.

- The Maldives are undoubtedly
fragile but one of the most beautiful places on the planet, and a place
to be loved and cherished now and in the future. Valentine’s Day
reminds us of love and maybe this year and beyond it’s good to
remember to love our planet.

Figure 53: A number of these
little islands can be seen in the image, with the turquoise colors
depicting clear shallow waters dotted by coral reefs and the red colors
highlighting vegetation on land. Different cloud formations can also be
seen, the difference in appearance is likely to be due to the different
height above the surface. This image, which was captured on 26 August
2015, is also featured on the Earth from Space video program (image credit: ESA, the image contains modified Copernicus Sentinel data (2015), processed by ESA, CC BY-SA 3.0 IGO)

• February 08, 2019: Captured on 1 October 2018 by the Copernicus Sentinel-2A satellite, the image of Figure 54 features part of northeast Kenya – an area east of the East African Rift Valley. 75)

- The region tends to be very arid
and this false-color image has been processed to highlight different
types of rock, soil and sand in pinks, purples and yellows.

- Part of the ‘great north
road’ can also been seen running from the bottom-left to the
top-right. The road is one of the best in the country, linking Nairobi
in the south of the country to Ethiopia. The northern 500-km stretch
from Isiolo to the Kenyan–Ethiopian border town of Moyale took
about nine years to build and was completed recently, but has reduced
travel time from Nairobi to Moyale from three days to about 12 hours
and opened up new opportunities for trade and business. Moyale can be
seen in the top-right of the image.

Figure 54:
The bright green at the top of the image depicts vegetation, but the
rest of the area appears relatively devoid of vegetation. Several dry
river beds can also be seen etched into the landscape and the black
shape in the middle-left appears to be an area of freshly burnt land.
The lack of water has, at times, led to clashes between clans over
access to water and pasture for cattle. When the rains do come,
however, this dry dusty land can burst into life and turn a rich green.
This Copernicus Sentinel-2A image is also featured on the Earth from Space video program (image credit: ESA, the image contains modified Copernicus Sentinel data (2018), processed by ESA, CC BY-SA 3.0 IGO)

• February 04, 2019: Wildfires
can cause devastation and are also to blame for more than a quarter of
greenhouse gases being released into the atmosphere. Satellites play a
key role in mapping landscape scarred by fire – but the
Copernicus Sentinel-2 mission has revealed that there are more fires
than previously thought. 76)

Figure 55: This Copernicus
Sentinel-2 image from 26 January 2019 shows fire-scarred land near the
Betty’s Bay area of Cape Town in South Africa. This false-color
image has been processed to show burned areas in dark greys and browns,
and areas covered with vegetation are shown in red [image credit: ESA,
the image contains modified Copernicus Sentinel data (2019), processed
by ESA, CC BY-SA 3.0 IGO] 77)

- From the vantage of space,
satellites can be used to detect fires and monitor how they spread and,
in the first instance, this can often help relief efforts. However,
satellites are also important for mapping the scars that fires leave in
their wake, particularly in remote regions.

- It is currently estimated that
fires contribute 25–35% of total annual greenhouse gas emissions
to the atmosphere so more precise information gained from
satellite-based scar-burn maps could help to better understand how they
add to the greenhouse effect.

- Land
disturbed by fire is an ‘essential climate variable’, which
are global datasets for the key components of Earth’s climate.

- Fire-scar mapping is also used
for managing natural resources, assessing fire risk and for adopting
mitigating strategies, for example.

- Thanks to Copernicus
Sentinel-2’s ability to zoom in on our planet, researchers have
discovered that there are more areas that are being affected by fire
than previously thought.

- A paper published recently in
Remote Sensing of the Environment describes how researcher used the
high-resolution imaging capability of the Copernicus Sentinel-2 mission
to produce the first detailed continental map of burns caused by
wildfires. 78)

- Sentinel-2 is a two-satellite
constellation built for the EU’s Copernicus environmental
monitoring program. Each identical satellite carries a high-resolution
multispectral imager. The mission has a myriad of uses, particularly
related to monitoring the health of world’s vegetation and
mapping how the surface of our land changes.

- The authors focussed on
sub-Saharan Africa as the region that accounts for around 70% of burned
area worldwide according to global satellite databases, making it the
ideal testbed for evaluating the potential for improving the
understanding of global impacts of fire.

Figure 56: Copernicus Sentinel-2 reveals more fires in Africa than thought. The authors of Ref. 78) focussed on sub-Saharan Africa and found that 4.9 million km2
of land had been burned in 2016 (left image), which is 80% more than
reported with information from coarser-resolution satellite sensors
(right image). These new-found areas comprised mainly burned areas
smaller than 100 ha (image credit: ESA, the image contains modified
Copernicus Sentinel data (2016), processed by the University of the
Basque Country–E. Roteta)

• January 25, 2019: Zaragoza
is the capital of the province of Zaragoza in the region of Aragon in
northeast Spain. It is home to about half of Aragon’s population,
making it the fifth largest municipality in Spain. 79)

Figure 57: This Copernicus
Sentinel-2B image features the city of Zaragoza nestling in the Ebro
valley and flanked by mountains to the south. The image was captured on
25 February 2018, it is also featured on the Earth from Space video program (image credit: ESA, the image contains modified Copernicus Sentinel data (2018), processed by ESA, CC BY-SA 3.0 IGO)

- In the top-right of the image,
the Ebro River can be seen winding its way through the city. Between
its source in the Cantabrian Mountains in the northwest and its delta
on the Mediterranean coast, the Ebro River is fed by more than 200
tributaries as it flows across much of northern Spain. In fact, the
Ebro River discharges more water into the sea than any other river in
Spain.

- In an otherwise arid region, the
river is used to irrigate crops in the valley – fields can be
seen in the top-right of the image.

- To the south of the city and
dominating the image, lie mountains, relatively devoid of vegetation.
There are also mountains to the north that are beyond the frame of this
image. These mountains, which effectively surround Zaragoza, form a
barrier to moisture from the Atlantic Ocean and from the Mediterranean
Sea, creating a semi-arid climate.

- On average,
Zaragoza only has about 350 mm of precipitation a year, compared to
Paris in France, for example, which has around 650 mm of precipitation
a year. In recent years, efforts – from discounts on water-saving
products to new watering systems for parks – have been in helping
to reduce water consumption. Efforts such as these resulted in
Zaragoza’s per capita use of water dropping from 150 liters/day
in 1997 to just 99 liters/day by 2012.

• January 18, 2019: The
Copernicus Sentinel-2 mission takes us over Gangotri, one of the
largest glaciers in the Himalayas and one of the main sources of water
for the Ganges River. 80)

- The Gangotri Glacier is in the
Indian Himalayan state of Uttarakhand. The head of the glacier can be
seen in the lower-right of the image near the Chaukhamba Peak. From
here, Gangotri flows around 30 km northwest, but like many of the
world’s glaciers it is in retreat. Studies suggest that Gangotri
has been receding for well over 200 years. Measurements have shown,
that it retreated by as much as 35 meters a year between the mid-1950s
and mid-1970s. While this has now reduced to about 10 meters a year,
observations show that the glacier is thinning.

- The glacier’s terminus is
called Gomukh, which means ‘mouth of a cow’, presumed to
describe what the snout of this huge glacier once resembled.
Importantly, the headwaters of the Bhagirathi River form here. In Hindu
culture and mythology, this is considered to be the source of the
Ganges River and consequentially the destination for many spiritual
pilgrimages and treks. Gomukh is a 20 km trek from the village of
Gangotri, which is in the top left of the image of Figure 58.
While Gomukh and Gangotri have much spiritual significance, the
Bhagirathi River offers an important supply of freshwater as well as
power as it passes through a number of power stations, including the
Tehri hydroelectric complex 200 km downstream (not pictured).

- Gangotri is in an area also known
as ‘the third pole’, which encompasses the Himalaya-Hindu
Kush mountain range and the Tibetan Plateau. The high-altitude ice
fields in this region contain the largest reserve of freshwater outside
the polar regions. With such a large portion of the world’s
population dependent on water from these cold heights, changes in the
size and flow of these glaciers can bring serious consequences for
society by affecting the amount of water arriving downstream.

- From the vantage point of space,
satellites, such as the Copernicus Sentinels, provide essential
information to monitor the changing face of Earth’s glaciers,
which are typically in remote regions and therefore difficult to
monitor systematically from the ground.

Figure 58: Sentinel-2 captured this image on 7 January 2018, it is also featured on the Earth from Space video program (image credit: ESA, the image contains modified Copernicus Sentinel data (2018), processed by ESA, CC BY-SA 3.0 IGO)

• January 11, 2019: The
Copernicus Sentinel-2B satellite takes us along the lower reaches of
the brown, sediment-rich Uruguay River. Here, the river forms the
border between Argentina and Uruguay and is the site of the Esteros de
Farrapos e Islas del Río Uruguay wetlands. 81)

- Composed of lagoons, swamps and
24 islets, the Esteros are a haven for wildlife, protected as a
national park and included on the List of Wetlands of International
Importance of the Ramsar Convention.

- This wetland system is home to
130 species of fish, 14 species of amphibian, 104 species of bird
– a quarter of all birds found in Uruguay – and 15 species
of mammal, including the maned wolf, the largest canid (meaning
dog-like) species in South America.

- A tourist attraction and a
waterway for transport, the Esteros also play an important role in
regulating flood levels and maintaining water quality, as well as
safeguarding the banks of the Uruguay River from erosion.

- Visible to the lower left –
its built structures shown in grey-white – is the Argentinian
town of Gualeguaychú. On the eastern shore of the Uruguay River
is the Uruguayan city of Fray Bentos, an important national harbor,
famous for a plant that once exported corned beef around the world. Now
inactive, this sprawling industrial complex has become a World Heritage Site.

- The dark green area to the east
of the Esteros is devoted to forestry, an important industry for the
region. A pulp mill is located close to Fray Bentos.

Figure 59: Sentinel-2B acquired this image of the Uruguay River wetlands on 17 August 2018, is also featured on the Earth from Space video program (image credit: ESA, the image contains modified Copernicus Sentinel data (2018), processed by ESA, CC BY-SA 3.0 IGO)

Sensor complement: (MSI)

MSI (Multispectral Imager):

The instrument is based on the
pushbroom observation concept. The telescope features a TMA (Three
Mirror Anastigmat) design with a pupil diameter of 150 mm, providing a
very good imaging quality all across its wide FOV (Field of View). The
equivalent swath width is 290 km. The telescope structure and the
mirrors are made of silicon carbide (SiC) which allows to minimize
thermoelastic deformations. The VNIR focal plane is based on monolithic
CMOS (Complementary Metal Oxide Semiconductor) detectors while the SWIR
focal plane is based on a MCT (Mercury Cadmium Telluride) detector
hybridized on a CMOS read-out circuit. A dichroic beamsplitter provides
the spectral separation of VNIR and SWIR channels. 82)83)84)85)86)87)88)

Airbus DS (former EADS Astrium SAS)
of Toulouse is prime for the MSI instrument. The industrial core team
also comprises Jena Optronik (Germany), Boostec (Bazet, France), Sener
and GMV (Spain), and AMOS, Belgium. The VNIR detectors are built by
Airbus DS-ISAE-e2v, while the French company Sofradir received a
contract to provide the SWIR detectors for MSI.

Calibration: A combination of
partial on-board calibration with a sun diffuser and vicarious
calibration with ground targets is foreseen to guarantee a high quality
radiometric performance. State-of-the-art lossy compression based on
wavelet transform is applied to reduce the data volume. The compression
ratio will be fine tuned for each spectral band to ensure that there is
no significant impact on image quality.

The observation data are digitized
on 12 bit. A shutter mechanism is implemented to prevent the instrument
from direct viewing of the sun in orbit and from contamination during
launch. The average observation time per orbit is 16.3 minutes, while
the peak value is 31 minutes (duty cycle of about 16-31%).

Figure 60: MSI instrument architecture (image credit: ESA)

Imager type

Pushbroom instrument

Spectral range (total of 13 bands)

0.4-2.4 µm (VNIR + SWIR)

Spectral dispersion technique

Dichroic for VNIR and SWIR split
In field separation within focal plane

Figure 63:
MSI spatial resolution versus waveleng: Sentinel-2’s span of 13
spectral bands, from the visible and the near-infrared to the shortwave
infrared at different spatial resolutions ranging from 10 to 60 m on
the ground, takes land monitoring to an unprecedented level(image
credit: ESA)

The filter-based pushbroom MSI
instrument features a unique mirror silicon carbide off-axis telescope
(TMA) with a 150 mm pupil feeding two focal planes spectrally separated
by a dichroic filter. The telescope comprises three aspheric mirrors:
M2 mirror is a simple conic surface, whereas the other mirrors need
more aspherization terms. The spectral filtering onto the different
VNIR and SWIR spectral bands is ensured by slit filters mounted on top
of the detectors. These filters provide the required spectral
isolation.

CMOS and hybrid HgCdTe (MCT)
detectors are selected to cover the VNIR and SWIR bands. The MSI
instrument includes a sun CSM (Calibration and Shutter Mechanism). The
1.4 Tbit image video stream, once acquired and digitized is compressed
inside the instrument.

The instrument carries one external
sensor assembly that provides the attitude and pointing reference (star
tracker assembly) to ensure a 20 m pointing accuracy on the ground
before image correction.

The detectors are built by Airbus
Defence and Space-ISAE-e2v: they are made of a CMOS die, using
0.35µm CMOS process, integrated in a ceramic package (Figure 64).
The VNIR detector has ten spectral bands, two of them featuring an
adjacent physical line allowing TDI operating mode, with digital
summation performed at VCU (Video and Compression Unit) level. On-chip
analog CDS (Correlated Double Sampling) allows to reach a readout noise
of the order of 130 µV rms. For each detector, the ten bands are
read through 3 outputs at a sample rate of 4.8MHz. The detector
sensitivity has been adjusted for each band through CVF (Charge to
Voltage conversion Factor) in view of meeting SNR specifications for a
reference flux, while avoiding saturation for maximum flux. A black
coating deposition on the non-photosensitive area of the CMOS die is
implemented to provide high straylight rejection.

The filter assemblies are procured
from Jena Optronik (JOP) in Germany. A filter assembly is made of
filter stripes (one for each spectral band) mounted in a Titanium
frame. The aims of the filter assembly are: i) to separate VNIR
spectral domain into the ten bands B1 to B9, ii) to prevent stray light
effects. This stray light limitation is very efficient since it is made
very close to the focal plane. Each filter stripe, corresponding to
each spectral band, is aligned and glued in a mechanical mount. A front
face frame mechanically clamps the assembly together.

The mechanical structure of MSI
instrument holds the 3 mirrors, the beam splitter device, the 2 focal
planes and 3 stellar sensors. It is furthermore mounted on the
satellite through 3 bolted bipods. This main structure (Figure 67) has a size of 1.47 m long x 0.93 m wide x 0.62 m high with a mass of only 44 kg.

The optical face of these mirror
blanks have been grounded by Boostec before and after CVD coating (i.e.
before polishing), with a shape defect of few tens of a µm. M1
and M2 are designed to be bolted directly on the main SiC structure. M3
is mounted on the same structure through glued bipods. 90)

Mirror

Shape

Mounting

Size (mm)

Mass

M1

aspheric of-axis concave

central fixture at back side

442 x 190

2.3 kg

M2

aspheric on-axis convex

central fixture at back side

147 x 118

0.3 kg

M3

aspheric of-axis concave

glued bipods on outer edges

556 x 291

5.1 kg

Table 9: MSI mirror characteristics

Mirror manufacturing: The mirror
optomechanical design was performed by EADS-Astrium on the basis of the
SiC-100 sintered silicon carbide from Boostec who produced the mirror
blanks and delivered them to AMOS (Advanced Mechanical and Optical
Systems), Liege, Belgium. AMOS is in charge of the deposition of a
small layer of CVD-SiC (Chemical Vapor Deposition-Silicon Carbide) on
the mirror. The purpose is to generate a non-porous cladding on the
mirror surface which allows the polishing process reaching a
microroughness state, compatible with the system requirements regarding
straylight. 91)

VNIR and SWIR focal plane
assemblies: Both focal planes accommodate 12 elementary detectors in
two staggered rows to get the required swath. The SWIR focal plane
operates at -80ºC whereas the VNIR focal plane operates at
20ºC. Both focal planes are passively cooled. A monolithic SiC
structure provides support to the detectors, the filters and their
adjustment devices and offers a direct thermal link to the radiator.

Figure 69: Focal plane configuration (image credit: EADS Astrium)

Filters and
detectors: Dedicated strip filters,mounted on top of each VNIR or SWIR
detector, provide the required spectral templates for each spectral
band. The VNIR detector is made of a CMOS die, using the 0.35 µm
CMOS technology, integrated in a ceramic package. The detector
architecture enables “correlated double.”

The so-called VNIR Filter Assembly
contains 10 VNIR bands (from 443 nm to 945 nm) and the so-called SWIR
Filter Assembly includes 3 SWIR bands (from 1375 nm to 2190 nm). The
sophisticated development of the filter assemblies is caused by the
specified spectral performance parameters and the high stray light
requirements due to the topology of the spectral bands. 92)

Sampling for the 10 VNIR spectral
bands along with TDI (Time Delay IntegrationI) mode for the 10 m bands.
Black coating on the die eliminates scattering.

The SWIR detector is made of an
HgCdTe photosensitive material hybridized to a silicon readout circuit
(ROIC) and integrated into a dedicated hermetic package. The SWIR
detector has three spectral bands for which the spectral efficiency has
been optimized. The B11 and B12 bands are being operated in (TDI) mode.

CSM (Calibration and Shutter Mechanism):
In MSI, the two functions of calibration and shutter are gathered in
one single mechanism to reduce mass, cost and quantity of mechanisms of
the instrument, increasing its reliability at the same time. The CSM is
located at the entrance of MSI, a rectangular device of ~ 80 cm x 30
cm, mounted on the frame of the secondary structure. The design and
development of the CSM is provided by Sener Ingenieria y Sistemas,
S.A., Spain. 93)

• During launch the CSM has to
protect the instrument from sun illumination and contamination by
covering the instrument entrance with a rectangular plate (named the
door). This is the close position, which has to be maintained under the
action of the launch loads.

• Once in orbit, the following functions are required from the CSM:

- To allow Earth observation to the
instrument (MSI) the door needs to rotate from the close position
63º inwards the instrument and maintain it stable without power.
This is the open position.

- From time
to time, in calibration mode of the MSI, the CSM inserts a sun diffuser
in front of the primary mirror and the sun diffuser is illuminated by
direct solar flux. This mode corresponds to a door position located
55º from the close position outward the instrument. This position
must be also stable without any power supply.

- In case of emergency, the CSM has
to rotate the door to the close position from any initial position to
prevent the sun light to heat sensible components of the instrument.
Similarly to the previous positions, the close position shall be stable
without power supply.

Figure 75: View of the CSM in calibration position (image credit: Sener)

A face to face ball bearing as
rotation axis hinge in the opposite side of the actuator is used
supported by means of an axially flexible support. Apart from that the
pinpuller mounted on a flexible support, holds the door during launch
by means of a cylindrical contact with respect to the door bushing.
This design is the result of the optimization made in order to reach a
stiff and robust but light and hyper-statically low constrained
mechanism to make it compatible under possible thermal environments.

The pinpuller provides a reliable launch locking device and allows after pin retraction the mechanism to rotate in both senses.

The MSI instrument design represents
state-of-the-art technology on many levels that is being introduced for
next generation European land-surface imagers. Obviously, its
performance will set new standards for future spaceborne multispectral
imagers.

Note: NAND (Not And) is a Boolean
logic operation that is true if any single input is false. Two-input
NAND gates are often used as the sole logic element on gate array
chips, because all Boolean operations can be created from NAND gates.

The NAND storage technology is not
only an established technology in commercial applications but
represents also a real and effective alternative for mass memory
systems in space. The main advantages of the NAND-Flash technology are:
a) the non-volatile data storage capability and b) the substantially
higher storage density.

In the commercial world the NAND
technology has become the preferred solution for storing larger
quantities of data on devices such as SSDs (Solid State Drives), USB
(Universal Serial Bus) Flash memory sticks, digital cameras, mobile
phones and MP3-Players. In the space business, this technology has been
used in some experiments only, but not in the frame of large scale mass
memory systems. This is now going to be changed. 94)95)96)

Astrium and IDA have continuously
worked for over seven years on the subject “NAND-Flash Technology
for Space”. In the frame of an ESA study dubbed SGDR (Safe Guard
Data Recorder) this NAND-Flash technology has been introduced and
intensively evaluated.

As a result of this extensive
testing, the radiation effects of this technology are well known
meanwhile and appropriate error handling mechanisms to cope with the
observed effects have been developed. For the S2 (Sentinel-2) mission,
a complete qualification program has been performed including radiation
tests, assembly qualification, construction analysis, electrical
characterization, reliability tests like burn-in, destructive physical
analysis, stress and life tests.

All these investments led to the
final conclusion that the selected SLC NAND-Flash is an adequate
technology for high capacity memory systems for space, even for systems
with very high data integrity requirements.

Table 10
lists some main requirements and provides in parallel the related
figures of two Astrium MMFU implementations. The first implementation
is based on SLC NAND-Flash devices and will be launched with the
Sentinel 2 satellite. The second option uses SDR-SDRAM devices, which
was the initially required baseline technology for this mission.

Parameter

Requirement

Astrium MMFU

NAND-Flash

SDR-SDRAM

User storage capacity

2.4 Tbit (EoL)

6 Tbit (BoL)

2.8 Tbit (BoL)

No of memory modules

-

3

11

Mass

≤ 29 kg

< 15 kg

< 27 kg

Max volume (L x H x W)

710 mm x 260 mm x 310 mm

345 mm x 240 mm x 302 mm

598 mm x 240 mm x 302 mm

Power (record & replay)

≤ 130 W

< 54 W

< 126 W

Power (data retention)

-

< 29 W (0 W)

< 108 W

Instrument input data rate

490 Mbit/s + 80 kbit/s (housekeeping)

Output data rate (downlink)

2 x 280 Mbit/s

Life time in orbit

up to 12.5 years

Reliability

≥ 0.98

0.988

> 0.98

Bit error rate (GCR) per day

≤ 9 x 10-13 / day

5.9 x 10-14 / day

< 9 x 10-13 / day

Table 10: Sentinel-2 MMFU requirements and resulting implementations

The related simplified architectural block diagram of the Astrium Sentinel-2 MMFU is shown in Figure 76.
The MMFU receives two parallel data streams either from the nominal or
redundant VCU (Video Compression Unit). The interfaces are
cross-strapped with redundant PDICs (Payload Data Interface
Controllers). After reception and adaptation to internal data formats
of the received source packets, the data is stored in memory modules.
FMM (Flash Memory Module) and respectively SMM for the SDR-SDRAM memory
module. For replay, the data is read out from two parallel operated
memory modules and routed via two active TFGs (Transfer Frame
Generators) providing interfaces for downlink and test. The system is
controlled by a Memory System Supervisor, which is based on an ERC32
processor. The required supply voltages are provided by a power
converter.

Figure 76: Architecture of the MMFU system (image credit: Astrium)

Each function is implemented by nominal and redundant hardware components. The functions and boards are summarized in Table 11:

Function

MMFU with NAND-Flash

MMFU with SDR-SDRAM

Modules (Functions)

Boards (Physical Assembly)

Modules (Functions)

Boards (Physical Assembly)

Memory System Supervisor

2

2

2

2

Payload Data Interface Controller

2

1

2

1

Memory Modules

3

3

11

11

Transfer Frame Generators

4

2

4

2

Power Converters

2

2

2

2

Total Board Count

10

18

Table 11: Number of functions and boards

Storage capacity: Astrium uses for
all boards a standard format. Therefore the maximum number of memory
and other devices which can be assembled on one board is limited by
this form factor. Both types of memory modules are nearly identical in
form, fit and function and because they can be mutually replaced; this
represents a good basis for comparison.

The selected NAND-Flash device
provides a capacity of 32 Gbit plus some spare. It is realized by means
of four 8 Gbit dies encapsulated in a standard TSOP1 package. In total,
the FMM (Flash Memory Module) includes 76 devices. The devices are
arranged in four partitions which can be independently powered. A
partition represents also the lowest level for reconfiguration. Each
partition contains sixteen devices to store user data and three devices
that are used to store parity information. This configuration enables
single symbol error correction and double symbol error detection.

The SDRAM based memory module has a
similar organization. There are also four partitions and each devices
for single symbol error correction. A device is represented by a stack
which contains eight SDRAM chips with a capacity of 512 Mbit each. From
this follows the user storage capacity per memory module and some other
parameters as listed in Table 12.

The number of FMM modules is
determined by the total data rate and the operational concept, which
requires the operation of two independent data streams. Therefore there
are two memory modules operated in parallel. The third one is provided
for redundancy.

The number of SMM modules is mainly
determined by the required capacity. Also here two modules are operated
in parallel and one SMM is included for reliability reasons.

The much higher storage density of
the NAND-Flash devices (factor of 8) leads to a massive reduction in
the number of required memory modules. For a mass memory system this
becomes especially evident, if there is a requirement for a large user
capacity as in case of the Sentinel-2 MMFU. Further positive aspects
evolve with reduction of the number of modules. The complete system
design from electrical and mechanical point of view is greatly relaxed.

Mass and volume:
With reduction of the number of memory modules, it is obvious that
directly related physical budgets like mass and volume, decline
accordingly. Mass is always a critical issue for space missions which
can be reduced by using NAND-Flash technology; but also the complete
system design of a satellite, in terms of mass, power, thermal and
other aspects, can be positively influenced by applying NAND-Flash
based memory systems. In case of the Sentinel-2 MMFU, indeed 14 Kg
(about 50%) can be saved.

Power: The power consumption is also reduced by more than 50% (Table 10).
This is mainly caused by the number of memory modules operated in
parallel. In case of Flash, there are only two active memory modules.
In case of the SDRAM technology, 10 memory modules are operated in
parallel: up to four modules for data access, two modules for read, two
modules for write, and all other modules in data retention mode. Data
retention means that the modules store user data and the SDRAM chips
have to be refreshed and scrubbed for error detection and correction.

In contrast, a Flash-based memory
module can be completely switched off without loss of data in the data
retention mode. For a minimum, the partitions can be switched off and
the power consumption of the controller part of the module is reduced
due to low activity.

It is not obvious, that, in all
cases, NAND-Flash consumes less power than SDR-SDRAM based systems. The
power consumption depends on several factors like required storage
capacity, data rates and operations. Generally it can be said, that as
long as the required storage capacity determines the number of memory
devices, Flash might be the better choice. If the number of memory
devices is determined by the required data rate, SDRAM based systems
may have a better performance from a power consumption point of view.

Data rates: Table 13
shows that SDR-SDRAM devices provide a much better performance from
data rate point of view. The overall performance of a memory module
depends on further characteristics like type of interfaces, memory
controller performance, and maximum power consumption and others.
Generally an SDRAM based memory module has advantages in terms of
access speed.

Performance parameter

SLC NAND-Flash

SDR-SDRAM

Die capacity (not stacked)

8 Gbit

512 Mbit

Operating voltage

2.7 V – 3.6 V

3.0 V – 3.6 V

Data bus width

8 bit

8 bit

Temperature range (std. available)

- 40ºC to + 85ºC

0ºC to +70ºC

Maximum read performance @ IO clock

< 250 Mbit/s @ 40 MHz on page level (4 k x 8)

< 800 Mbit/s @ 100 MHz burst operation

Erase time

2 ms on block level (256 k x 8)

N/A

Endurance

> 105

∞

Data retention

10 years

N/A

Table 13: Performance characteristics of the memory devices

The lower performance of NAND-Flash
is determined by three characteristics. During writing the NAND-Flash
devices need to be programmed and this takes a time of about 700
µs per 4 kbyte data (one device page). Additionally the so-called
blocks of a NAND-Flash device have to be erased before programming.
This consumes another 2 ms per block (64 pages). Last but not least,
the selected NAND-Flash devices use an eight bit interface for serial
commanding, addressing and data transfer with a maximum operating
frequency of 40 MHz.

This lack in performance can be
mitigated by mainly two measures. The first straight forward measure is
parallel operation of NAND-Flash devices. The second measure is
interleaved access to several NAND-Flash devices. Interleaving uses the
programming time of a NAND-Flash device to write in parallel the next
device. These methods allow increasing the write access performance.

Life time and reliability:
NAND-Flash devices provide a limited endurance. This is caused by an
inherent wear out mechanism of the Flash memory cells which limits the
number of erase and write cycles to about 105 cycles. To mitigate the
endurance limitation, most Flash memory systems are equipped with an
address management system, which distributes the write accesses rather
uniformly over the address space. This technique is called Wear
Leveling.

Furthermore the very high device
capacity of NAND-Flash devices offers the opportunity to implement a
physical address space, which exceeds the required logical user address
space by a factor of n. This enhances the wear out limit of the logical
addresses by the factor of n too. Hence there are two methods to keep
the total count of write accesses to the same physical address below
the wear out limit.

Radiation and error rates: In
general, sensitivity of electronic devices to space radiation is a
major topic and is also shortly discussed here through a comparison of
NAND-Flash and SDR-SDRAM devices.

The mass memory system based on
NAND-Flash shows clear advantages and fits well to the high storage
capacity and moderate data rates of the Sentinel-2 application. The
very high storage density of the NAND-Flash devices leads to a reduced
number of memory modules with advantages in terms of power consumption,
mass and volume. Furthermore this feature improves the reliability and
eases the system design from mechanical and electrical points of view.

For Copernicus operations, ESA has
defined the concept and architecture for the Copernicus Core ground
segment, consisting of a Flight Operations System (FOS) and a Payload
Data Ground Segment (PDGS). Whereas the flight operations and the
mission control of Sentinel-1 and -2 is performed by ESOC (ESAs
European Space Operations Center in Darmstadt, Germany), the operations
of Sentinel-3 and the Sentinel-4/-5 attached payloads to meteorological
satellites is performed by EUMETSAT.

The ground segment includes the following elements:

• Flight Operations Segment
(FOS): The FOS is responsible for all flight operations of the
Sentinel-2 spacecraft including monitoring and control, execution of
all platform activities and commanding of the payload schedules. It is
based at ESOC, Darmstadt in Germany and comprises the Ground Station
and Communications Network, the Flight Operations Control Centre and
the General Purpose Communication Network.

• Payload Data Ground Segment
(PDGS): The PDGS is responsible for payload and downlink planning, data
acquisition, processing, archiving and downstream distribution of the
Sentinel-2 satellite data, while contributing to the overall monitoring
of the payload and platform in coordination with the FOS.

The Service Segment, geographically
decentralized, will utilize the satellite data in combination with
other data to deliver customized information services to the final
users.

The baseline ground station network
will include four core X-band ground stations for payload observation
data downlink and one S-band station for Telemetry, Tracking and
Control (TT&C). To a limited extent, the system can also
accommodate some direct receiving local user ground stations for
Near-Real Time applications.

The systematic activities of the
PDGS include the coordinated planning of the mission subsystems and all
processes cascading from the data acquired from the Sentinel-2
constellation, mainly:

1) The automated and recurrent
planning of the satellite observations and transmission to a network of
distributed X-band ground stations

2) The systematic acquisition and
safeguarding of all spacecraft acquired data, and its processing into
higher level products ensuring quality and timeliness targets

3) The recurrent calibration of the instrument as triggered by the quality control processes

4) The automated product
circulation across PDGS distributed archives to ensure the required
availability and reliability of the data towards users

5) The long-term archiving of all mission data with embedded redundancy over the mission lifetime and beyond.

EDRS (European Data Relay Satellite)
will provide a data relay service to Sentinel-1 and -2 and initially is
required to support 4 Sentinels simultaneously. Each Sentinel will
communicate with a geostationary EDRS satellite via an optical laser
link. The EDRS GEO satellite will relay the data to the ground via a
Ka-band link. Optionally, the Ka-band downlink is planned to be
encrypted, e.g. in support to security relevant applications. Two EDRS
geo-stationary satellites are currently planned, providing in-orbit
redundancy to the Sentinels. 99)

EDRS will provide the same data at
the ground station interface as is available at the input to the OCP
(Optical Communications Payload) on-board the satellites, using the
same interface as the X-band downlink. The EDRS transparently adapts
the Sentinels data rate and format to the internal EDRS rate and
formats, e.g. EDRS operates at bit rates of 600 Mbit/s and higher.

With EDRS, instrument data is
directly down-linked via data relay to processing and archiving
centers, while other data continues to be received at X-band ground
stations. The allocation of the data to downlink via X-band or EDRS is
handled as part of the Sentinel mission planning system and will take
into account the visibility zones of the X-band station network and
requirements such as timeliness of data.

Figure 81: Sentinel missions - EDRS interfaces (image credit: ESA)

Copernicus / Sentinel data policy:

The principles of the Sentinel data policy, jointly established by EC and ESA, are based on a full and open access to the data:

• anybody can access acquired
Sentinel data; in particular, no difference is made between public,
commercial and scientific use and in between European or non-European
users (on a best effort basis, taking into consideration technical and
financial constraints);

• the licenses for the Sentinel data itself are free of charge;

• the Sentinel data will be
made available to the users via a "generic" online access mode, free of
charge. "Generic" online access is subject to a user registration process and to the acceptation of generic terms and conditions;

•
additional access modes and the delivery of additional products will be
tailored to specific user needs, and therefore subject to tailored
conditions;

The objective of ESA’s SEOM (Scientific Exploration of Operational Missions) Program Sen2Coral
is the preparation of the exploitation of the Sentinel-2 mission for
coral reefs by developing and validating appropriate, open source
algorithm available for the community. The project objectives are the
scientific exploitation and validation of the Sentinel-2 MSI
(Multispectral Instrument) for mapping (habitat, bathymetry, and water
quality) and detection change for coral reef health assessment and monitoring, and algorithm development dedicated to Sentinel-2 capabilities to satisfying these objectives. 105)

To address the extremely interesting
and challenging questions posed by this project a consortium of
contractors with appropriate background knowledge and skills has been
assembled. The consortium comprises:

• ARGANS Limited, UK

• CNR-IREA, Italy

• CS-SI, France

The consortium is complimented by a
science team of consultants and partners who are recognized
international scientists in the field.

Research Program:

• A critical analysis of
feedback from scientists and institutions collected through
consultations in ESA and Third Party workshops, symposia and
conferences.

Tropical coral reefs are globally
important environments both in terms of preservation of biodiversity
and for the substantial economic value their ecosystem services provide
to human communities. Managing and monitoring reefs under current
environmental threats requires information on their composition and
condition, i.e. the spatial and temporal distribution of benthos and
substrates within the reef area. Determining the relative abundance of
biotic types such as coral and macroalgae is the key for detecting and
monitoring important biotic changes such as phase or regime shifts due
to changes in environmental conditions. Coral bleaching events, where
stressed corals expel their symbiotic algae and turn white in color,
can provide indications of anthropogenic stressors and climate change
impacts, while subsequent coral mortality may be a key determinant of
future reef state. In addition to monitoring of current status, maps of
benthos have the potential to inform management decisions such as the
placement of marine protected areas and could in the future be used to
seed models to predict ecosystem dynamics.

Background: The degradation of coral
reefs is a fact, with 55% of reefs being affected by overfishing and
destructive fishing methods, which as the most pervasive threats,
whereas 25% of reefs are affected by coastal development and pollution
from land, including nutrients from farming and sewage, while one tenth
suffer from marine-based pollution (local pressures are most severe in
South-East Asia, where nearly 95 per cent of coral reefs are
threatened).

In addition the coral reefs’
ecosystems appear to be the first to respond to global climate changes,
such as increased sea surface temperature (SST), ultraviolet radiation
(UV) and acidification of seawater that results from higher levels of
atmospheric CO2 concentration.

Sentinel-2 MSI Data Acquisition:

The MSI (Multispectral Instrument)
of the Sentinel-2A mission offers several potential technical
advantages in the remote sensing of coral reefs due to:

The objective “to develop and
validate new algorithms relevant for coral reef monitoring based on
Sentinel-2 observations” will be addressed by parameterizing
existing models for processing hyper-spectral & multi-spectral data
and developing pre-processors for these models to build Sentinel-2 data
processing algorithms for the retrieval of coral reefs’ static
and dynamic characteristics. The code developed will be made available
open source.

To design, verify and validate three
coral reef monitoring products making the best use of Sentinel-2 MSI
mission characteristics:

• Habitat mapping of coral reefs

• Coral reef change detection

• Bathymetry over coral reefs.

Field Campaign:

A 6 day field campaign around the
South Pacific island of Fatu Huku was undertaken by French scientist
Antoine Collin to collect in-situ data to test and validate the
capabilities of the Sentinel-2 satellite to monitor coral reef
bleaching.

Fatu Huku Island in French Polynesia
was chosen as the survey site because of the presence of developed
coral reefs and it is an area water temperatures are high as a result
of the current El Niño event. During the survey, water
temperature exceeding 30°C were recorded and coral bleaching, the
expulsion of the symbiotic algae that provide energy from sunlight to
the coral, was observed to be taking place.

Data collected from this field
campaign complements archives of in-situ data collected over previous
years from coral reef sites across the globe such as at Heron Island
and Lizard Island, in Australia, and reefs around Palau, in the western
Pacific Ocean.

The information compiled and edited in this article was provided byHerbert
J. Kramer from his documentation of: ”Observation of the Earth
and Its Environment: Survey of Missions and Sensors” (Springer
Verlag) as well as many other sources after the publication of the 4th
edition in 2002. - Comments and corrections to this article are always
welcome for further updates (herb.kramer@gmx.net).